1709 lines
92 KiB
Plaintext
1709 lines
92 KiB
Plaintext
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FELINE GENETICS
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R. Roger Breton
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Nancy J Creek
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------------------------------
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Cells, Chromosomes, and Genes
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From a 35-pound Main Coon to a 5-pound Devon Rex; from the small
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folded caps of a Scottish Fold to the great, delicate ears of a Bali-
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nese; from the 4-inch coat of a Chinchilla Persian to the fuzzy down
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of a Sphinx; from the deep Ebony of a Bombay to the translucent white
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of a Turkish Angora; from the solid color of a Havana Brown to the
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rich tabbiness of a Norwegian Forest Cat: the variety and beauty to
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be found in the domestic cat is beyond measure. When these character-
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istics are coupled with the genetically-patterned and environmentally-
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tailored personalities of the individuals, it can be seen that each
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animal is as unique as it is possible to be. There truly is a cat for
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everyone.
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Wide as the range of cats is, it pales when compared with the varie-
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ties of Other Pet. Why should the dog exhibit such a wide spectrum of
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body types, looking like completely different creatures in some cases,
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while cats always look like cats (as horses always look like horses)?
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The secrets behind the wide variations in possible cats, and why cats,
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unlike dogs, resist gross changes and always look like cats, can be
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found in its genetic makeup.
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In order to understand what happens genetically when two cats do their
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thing, it is necessary to understand a few basic things about genetics
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in general. To study genetics, is to study evolution in miniature,
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for it is through the mechanism of genetics that evolution makes
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itself felt. In chapter 1, we showed how the gross evolution of the
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cat came about, and how this gross mechanism was applied to the Euro-
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pean Wildcat to evolve the African Wildcat, the immediate forerunner
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of our cats. We will examine this mechanism itself to better under-
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stand how the first domestic cat has become the dozens of breeds
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available today, and how cat breeders use this mechanism to create new
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breeds or improve existing ones.
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Cats, like people, are multi-cellular creatures: that is, their
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bodies are composed of cells, lots and lots of cells. Unlike primi-
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tive multicellular creatures, cat bodies are not mere colonies of
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cells, but rather societies of cells, with each type of cell doing a
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specific task. To one specific type of cells, the germ cells (ova in
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females and sperm in males), fall the task of passing the genetic code
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to the next generation. The method the Great Engineer has developed
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to carry this out is one of the most awesome, most elegant, and most
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beautiful processes in nature.
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The cells of a cat, with few special exceptions, are eukaryotic, that
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is, they have a membrane surrounding them (acting as a sort of skin),
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are composed of cytoplasm (cell stuff) containing specialized orga-
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----------------------------------------------------------------------
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Feline Genetics Page 1
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nelles (the parts that do the cell's task), and have an inner membrane
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surrounding a nucleus. It is this nucleus that contains all the
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genetic materials.
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Within the nucleus of a cell are found the chromosomes, long irregular
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threads of genetic material. These chromosomes are arranged in pairs:
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19 pairs in a cat, 23 pairs in a human. It is these 38 chromosomes
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that contain the "blueprint" for the individual cat.
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When inspected under a microscope, the chromosomes reveal irregular
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light and dark bands: hundreds of thousands, perhaps millions per
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chromosome. These light and dark bands are the genes, the actual
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genetic codes. Each gene controls a single feature or group of fea-
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tures in the makeup of the individual. Many genes interact: a single
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feature may be controlled by one, two, or a dozen genes. This makes
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the mapping of the genes difficult, and only a few major genes have
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been mapped out for the cat.
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The chromosome is itself composed primarily of the macromolecule DNA,
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(deoxyribonucleic acid): one single molecule running the entire
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length of the chromosome. DNA is a double helix, like two springs
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wound within each other. Each helix is composed of a long chain of
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alternating phosphate and deoxyribose units, connected helix to helix
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by ladder-like rungs of four differing purine and pyridamine com-
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pounds.
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It is not the number of differing compounds that provide the secret of
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DNA's success, but rather the number of rungs in the ladder (uncounted
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millions) and the order of the amino acids that make up the rungs.
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The four different amino acids are arranged in groups of three, form-
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ing a 64-letter alphabet. This alphabet is used to compose words of
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varying length, each of which is a gene (one particular letter is
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always used to indicate the start of a gene). Each gene controls the
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development of a specific characteristic of the lifeform. There is an
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all-but-infinite number of possible genes. As a result, the DNA of a
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lifeform contains its blueprint, no two alike, and the variety and
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numbers of possible lifeforms has even today barely begun.
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Mitosis and Mendel
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When a cell has absorbed enough of the various amino acids and other
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compounds necessary, it makes another cell by dividing. This process
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is called mitosis, and is fundamental to life.
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Not too long ago, it was thought that the chromosomes were generated
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immediately prior to mitosis, and dissolved away afterwards. This
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turned out not to be true. The extremely tiny chromosomes, normally
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invisible in an optical microscope, shorten and thicken during mito-
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sis, becoming visible temporarily.
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The rather complex process of mitosis can perhaps be explained simply
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as a step-by-step process:
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Mitosis begins when the cell senses sufficient growth and nutrients to
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----------------------------------------------------------------------
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Feline Genetics Page 2
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support two cells.
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The invisible chromosomes duplicate themselves through the wonder of
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DNA replication. Various enzymes are used as keys to unlock and
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unwind the double helix into two single helices. Each of these he-
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lices then uses other enzymes to lock the proper parts (the amino
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acids and other stuff) together to build a new second helix, complete
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with all transverse rungs, so that the results will be exact replicas
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of the original double helix. This winding and unwinding of the DNA
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can take place at speeds up to 1800 rpm! The two daughter chromosomes
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remain joined at a single point, called the centromere.
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The cromosomes then wind themselves up, shortening and thickening,
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making them visible under the microscope, and attach themselves to the
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nuclear membrane.
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The nuclear membrane then dissolves into a fibrous spindle, with at
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least one fiber passing through each centromere (there are many more
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fibers than centromeres).
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The fibers then stretch and pull the centromeres apart, pulling the
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chromosomes to opposite sides of the cell.
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The spindles dissolve into two new nuclear membranes, one around each
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group of chromosomes.
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The chromosomes unwind back into invisibility, the cell divides, and
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mitosis is complete. Genetically, each daughter cell is an exact
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duplicate of the parent cell.
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Since the genetic coding is carried in the rungs of the DNA and only
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consists of four different materials arranged in groups of three to
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form words of varying length written with a 64-letter alphabet, the
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instructions for a "cat" may be considered to consist of two sets of
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19 "books," each millions of words long, one set from each of the
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cat's parents. The numbers of possible instructions are more than
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astronomical: there are far more possible instructions in one single
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chromosome than there are atoms in the known universe!
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A single gene is a group of instructions of some indeterminate length.
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Somewhere among all the other codes is a set of instructions composing
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the "white" gene, and what that set says will determine if the cat is
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white or non-white.
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Since a cat receives two sets of instructions, one from each parent,
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what happens when one parent says "make the fur white" and the other
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says "make the fur non-white"? Will they effect a compromise and make
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the fur pastel? No, they will not. Each and every single gene has at
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least two levels of expression (many have more), called alleles, which
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will determine the overall effect. In the case given, the "make the
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fur white" allele, "W", is dominant, while the "make the fur non-
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white" allele, "w", is recessive. As a result, the fur may be white
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or non-white, not pastel (we're only speaking of the "white" gene
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here, a gray cat is caused by an entirely different gene).
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Feline Genetics Page 3
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In order to understand how this works, lets run through a couple of
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simple examples using the white gene. A cat has two and only two
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white genes. Since each white gene, for the purposes of our examples,
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consists of one of two alleles, "W" or "w", a cat may have one of four
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possible karyotypes (genetic codes) for white: "WW", "Ww", "wW",
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"ww". Since "W" is dominant to "w", the codes "WW", "Ww", and "wW"
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produce white cats, while the code "ww" produces a non-white cat.
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| W w
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--+--------
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W | WW Ww
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w | wW ww
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The double-dominant "WW" white cat has only white alleles in its white
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genes. It is classed as homozygous (same-celled) for white, and will
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produce only white offspring, regardless of the karyotype of its mate.
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The single-dominant "Ww" or "wW" white cat has one of each allele in
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its white genes. It is classed as heterozygous (different-celled) for
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white, and may or may not produce white offspring, depending upon the
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karyotype of its mate.
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The recessive "ww" non-white cat has only non-white alleles in its
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white genes. It is classed as homozygous for non-white, and may or
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may not produce white offspring, depending upon the karyotype of its
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mate.
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Assuming these cats mate, there are sixteen different possible karyo-
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type combinations. Since each cat in these sixteen combinations will
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pass on to their offspring one and only one allele, there are four
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possible genetic combinations from each mating. There are sixty-four
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possible combinations of offspring.
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| WW | Ww | wW | ww
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| W W | W w | w W | w w
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------+--------+--------+--------+--------
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WW W | WW WW | WW Ww | Ww WW | Ww Ww
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W | WW WW | WW Ww | Ww WW | Ww Ww
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------+--------+--------+--------+--------
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Ww W | WW WW | WW Ww | Ww WW | Ww Ww
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w | wW wW | wW ww | ww wW | ww ww
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------+--------+--------+--------+--------
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wW w | wW wW | wW ww | ww wW | ww ww
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W | WW WW | WW Ww | Ww WW | Ww Ww
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------+--------+--------+--------+--------
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ww w | wW wW | wW ww | ww wW | ww ww
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w | wW wW | wW ww | ww wW | ww ww
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Inspecting these possible offspring, several patterns emerge. Of the
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64 possible offspring, 16, or exactly one-quarter, have any given
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pattern. This means that one quarter of all possible matings will be
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homozygous for white, "WW", two quarters will be heterozygous for
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white, "Ww" or "wW" (which are really the same thing), and one quarter
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----------------------------------------------------------------------
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Feline Genetics Page 4
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will be homozygous for non-white, "ww". Since homozygous white and
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heterozygous white will both produce white cats, three-quarters of all
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possible combinations will produce white cats, and only one-quarter
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will produce non-white cats. This 3:1 ratio is known as the Mendelian
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ratio, after Gregor Johann Mendel, the father of the science of genet-
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ics.
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Further inspection leads us to several conclusions. If a homozygous
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white cat mates, all offspring will be white. If two homozygous white
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cats mate, all offspring will be homozygous white. If a homozygous
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white cat mates with a heterozygous white cat, there will be both
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homozygous white and heterozygous white offspring in a 1:1 ratio. If
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a homozygous white cat mates with a homozygous non-white cat, all
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offspring will be heterozygous white. Thus, a homozygous white cat
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can only produce white offspring, regardless of the karyotype of its
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mate, and is said to be true breeding for white.
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If two heterozygous white cats mate, there will be homozygous white,
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heterozygous white, and homozygous non-white offspring in a ratio of
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1:2:1. The ratio of white to non-white offspring is the Mendelian
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ration of 3:1. If a heterozygous white cat mates with a homozygous
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non-white cat, there will be both heterozygous white and homozygous
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non-white offspring in a 1:1 ratio.
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If two homozygous non-white cats mate, all offspring will be homozy-
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gous non-white. Homozygous non-white cats are therefore true-breeding
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for non-white when co-bred.
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Geneticists differentiate between what a cat is genetically versus
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what it looks like by defining its genotype versus its phenotype. A
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homozygous white cat has a white genotype and a white phenotype.
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Likewise, a homozygous non-white cat has a non-white genotype and a
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non-white phenotype. A heterozygous white cat, on the other hand, has
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both a white genotype and a non-white genotype, but only a white
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phenotype.
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Naturally, in a given litter of four kittens the chances of having a
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true Mendelian ratio are slim (slightly better than 1:11), so several
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generations of pure white kittens could be bred, still carrying a
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recessive non-white allele. In all good faith you then breed your
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several-generations-all-white-but-heterozygous female to a similar
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several-generation-all-white-but heterozygous male and voila! A black
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kitten! The non-white genotype has finally shown itself.
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This Mendelian patterning is the basic rule of genetics. Since the
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rule is so simple, why is it so hard to predict things genetically?
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The reason is that we are dealing with more than one gene from each
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parent. The number of possible offspring combinations is two to the
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power of the number of genes: one gene from each parent is two genes,
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two squared is four possibilities; two from each parent is four, two
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to the fourth is sixteen; three from each is six, two to the sixth is
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64;... There are literally hundreds of millions of genes for one cat,
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yet a mere hundred from each parent produces a 61-digit number for the
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Feline Genetics Page 5
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possible offspring combinations!
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Meiosis
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Since each cell contains the entire chromosome set, 19 pairs, how is
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it possible for a parent to pass on only the genes from one chromosome
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of a pair, and not both. This is accomplished via the gametes: the
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germ cells, ova for females and sperm for males. Within the gonads
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(ovaries or testes), these special cells go through a division process
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known as meiosis.
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Unlike the normal process of mitosis, where the chromosomes are faith-
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fully replicated into duplicates of themselves, in meiosis the result-
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ant gametes have only half the number of chromosomes, one from each
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original pair. This involves a double division.
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As in mitosis, meiosis begins when the cell senses sufficient growth
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and nutrients to support division. The invisible chromosomes are
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duplicated through DNA replication. As usual, the two daughter chro-
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mosomes remain joined at the centromere. The chromosomes wind them-
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selves up, shortening and thickening, becoming visible under the
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microscope. Each new chromosome twin aligns itself with its homolo-
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gous counterpart: the twin chromosome from its opposite number in the
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original chromosome pair. The two twin chromosomes intertwine into a
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tetrad and exchange genes in a not clearly understood process that
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randomizes the genes between the twins. The tetrad attaches itself to
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the nuclear membrane. The nuclear membrane dissolves into a spindle,
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with at least one fiber passing through both centromeres of each
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tetrad. The fibers stretch and pull the tetrads apart, pulling the
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chromosomes twins to opposite sides of the cell. Once the chromosome
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twins are at the poles of the spindle, the spindle dissolves and
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reforms as two separate parallel spindles at right angles to the
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original spindle, with at least one fiber through each centromere. At
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this time there are effectively two mitoses taking place. The paral-
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lel spindles pull the centromeres apart, forming four separate groups
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of chromosomes, each of which consists of one-half the normal number.
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The spindles dissolve and four new nuclear membranes form, one around
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each group of chromosomes. The chromosomes unwind back into invisi-
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bility, the cell divides into four gametes, each having 19 chromo-
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somes, and meiosis is complete.
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At the moment of conception, a single sperm penetrates a single ovum,
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the ovum absorbs the sperm, merging the sperm's nucleus with its own
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and pairing the two sets of chromosomes. The ovum has now become a
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zygote, which begins dividing through the normal mitosis process, and
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a kitten is on its way.
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Male, Female, and Maybe
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The 19 pairs of chromosomes in a cat carry the numbers 1 through 18,
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plus "X" and "Y". The "X" and "Y" chromosomes are very special, for
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they determine the sex of the kitten. A female cat has two "X" chro-
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mosomes, "XX", while a male cat has one "X" and one "Y" chromosome,
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"XY", so if we follow the Mendelian pattern for sex determination we
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Feline Genetics Page 6
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find that the female parent can provide only an "X" chromosome to her
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offspring, while the male parent can provide either an "X" chromosome
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or a "Y" chromosome. The resulting kittens are either "XX" or "XY",
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as determined by the father. The same rule also applies to people
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(Sorry guys, if you and the wife have seven girls, it's your fault,
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not hers!).
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Since the sex chromosomes follow the same rules as the other chromo-
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somes, why bother mentioning them separately? Because they don't
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exactly follow the same rules: the "X" chromosome is longer than the
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"Y" chromosome, and it is this extra length that carries the codes for
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the female. When there is only one set of these extra codes, they act
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as recessives, allowing the male characteristic to dominate. When
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there are two sets, they act as dominants, and suppress the male
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characteristics. Thus, female and male kittens.
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We could end the argument here if it weren't for two complications.
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First, the extra-length of the "X" chromosome carries some genes that
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are for other than sex characteristics (such as the gene for orange
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fur): such characteristics are said to be sex-linked, and operate
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differently in males and females.
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A further complication comes with incomplete separation of the "X"
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gene twin at the centromere. An "X-X" gene twin has its centromere
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exactly where "Y"'s would become "X"'s. If an "X" were to fracture at
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the centromere during the process of separation, it would become an
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effective "Y". This is rare but by no means unheard of, and produces
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a "false" "Y" (shown as "y" to differentiate it from a female "XX"
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parent.
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Another variation is incomplete separation, where only a "false cen-
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tromere" is separated from the gene twin, with or without a part of
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the twin, causing one gamete to have 18 chromosomes (neither an "X" or
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a "y" while the other has 20 (either two "X"'s, an "Xy", or two "y"'s,
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depending on the point and angle of fracture).
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These variations on the sex chromosomes mean that a female, being "XX"
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in nature, can produce ova with the following: "XX", "Xy", "yy", "X",
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"y", or "O" (no sex chromosome). A male, being "XY", can produce
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sperm with "XY", "Yy", "X", "Y", "y", or "O". A zygote, taking one
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gamete from each parent, may then be any of the following 36 possibil-
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ities:
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| XX Xy yy X y O
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---+--------------------------------
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XY | XXXY XXYy XYyy XXY XYy XYO
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Yy | XXYy XYyy Yyyy XYy Yyy YyO
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X | XXX XXy Xyy XX Xy XO
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Y | XXY XYy Yyy XY Yy YO
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y | XXy Xyy yyy Xy yy yO
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O | XXO XYO yyO XO yO OO
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Since at least one "X" is required (can't build a puzzle without all
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the pieces), we may immediately ignore "Yyyy", "Yyy", "yyy", "YyO",
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----------------------------------------------------------------------
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Feline Genetics Page 7
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"yyO", "Yy", "yy", "YO", "yO", and "OO".
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In a like manner, "XXXY", "XXYy", and "XYyy" have too many pieces and
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are unstable, usually dying at conception, in the womb, or soon after
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birth (and invariably before puberty) from gross birth defects due to
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over-emphasis of various sex-linked traits.
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Turner females, "XO", show all normal female characteristics save that
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they have difficulty reproducing due to the absence of a paired sex
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chromosome, which inhibits normal meiosis.
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Kleinfelter superfemales, "XXX", tend to exhibit an unusually strong
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maternal instinct, often refusing to wean or surrender their young.
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This leads to psychological damage in the young, usually resulting in
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antisocial behavior.
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Kleinfelter supermales, "XYy" or "Xyy", tend to exhibit a generally
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antisocial behavior, often leading to unnecessary fighting to the
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point of inhibiting mating. As an interesting aside, among us humans
|
||
approximately 5 per cent of convicted male felons are supermales.
|
||
Hermaphrodites, "XXy" and "XXY", have male bodies but tend to exhibit
|
||
various female characteristics, often adopting orphan kittens or other
|
||
young. One such cat adopted a litter of mice, which it lovingly
|
||
raised while gleefully hunting their relatives. Hermaphrodites are
|
||
invariably sterile, sometime having both sets of sexual organs with
|
||
neither fully developed. This is the most common of the aberrant
|
||
sexual makeups.
|
||
|
||
Pseudoparthenogenetic females, "XXO", or males, "XYO", are identical
|
||
to normal cats in every way save that their sex and sex-linked charac-
|
||
teristics come only from one parent.
|
||
|
||
Gene-reversal males, "Xy", suffer partial gene reversal, receiving a
|
||
normal "X" from one parent and a "y" from the other parent's "X".
|
||
This is the rarest of the aberrant sexual makeups.
|
||
|
||
Pseudoparthenogenetic and gene-reversal animals often suffer from
|
||
birth defects and other signs of the aberrant genetic construct.
|
||
|
||
Normal females, "XX", and males, "XY", are by definition the norm and
|
||
vastly outnumber all other type combined. Chances are less than
|
||
1:10000 that any given cat has a genetically aberrant sexual makeup,
|
||
the most common of which is hermaphroditism, about 1:11000.
|
||
|
||
Mutations
|
||
|
||
Going back to genes in general, those genes that are found in the
|
||
African Wildcat, felis lybica, the immediate ancestor of our cats, are
|
||
termed "wild." These genes may be considered to be the basic stock of
|
||
all cats.
|
||
|
||
Since all cats do not look like African Wildcats (brown tabbies), it
|
||
is obvious that some changes have taken place in the genetic codes.
|
||
These changes occur all the time, and are called mutations. Unlike
|
||
|
||
|
||
----------------------------------------------------------------------
|
||
Feline Genetics Page 8
|
||
|
||
|
||
|
||
|
||
the distortions shown in cheap post-apocalypse or ecological-disaster
|
||
movies, mutations rarely occur at the gross level, but rather at the
|
||
level of the genetic codes themselves.
|
||
|
||
Mutations occur when, in the course of mitosis or meiosis, there is an
|
||
imperfect replication or joining of the components of the DNA macro-
|
||
molecule. Such imperfections can occur as a result of a chemical
|
||
imbalance within the body which affects replication. Most commonly
|
||
these days such an imbalance is caused by the introduction of some
|
||
foreign agent into the body (such as nicotine or, for an extreme
|
||
example, thalidomide) which acts as a catalyst and affects the keying
|
||
action of the enzymes during replication. Such agents are called
|
||
mutagens.
|
||
|
||
The greatest of all mutagens is radiation. It is believed that the
|
||
vast majority of spontaneous mutations, such as extra toes, long hair,
|
||
albinism, etc., that keep reoccurring in an otherwise clean gene pool
|
||
are caused by solar radiation, cosmic rays, the Earth's own background
|
||
radiation, and most probably, by radioactive isotopes of the atoms
|
||
making up DNA itself, most significantly carbon-14. (One of the
|
||
dangers of nuclear war, other than the obvious, is that the increase
|
||
in background radiation and atmospheric carbon-14 may increase the
|
||
numbers of spontaneous mutations to the point where the germ cells
|
||
lose viability, and whole species, even genera, would go the way of
|
||
the dinosaur.)
|
||
|
||
Mutations are the very essence of evolution (or of a breeding program,
|
||
which is merely evolution guided by man). It is through mutation that
|
||
the survival of the fittest takes place.
|
||
|
||
To illustrate this, let's assume a species of striped cat living on
|
||
the plains. He undergoes a mutation creating a spotted coat (the
|
||
stripes get broken up). For our plains friend, the spots don't blend
|
||
as well as stripes with the long shadows and colors of the grasses,
|
||
his prey can see and avoid him better, and he soon evolves out. This
|
||
was a detrimental mutation (most are).
|
||
|
||
Now let's assume the same species of striped cat living in woodlands.
|
||
He undergoes the same mutation creating a spotted coat. In his case,
|
||
the spots blend better with the dapple of light and shadow playing
|
||
through the trees, his prey can't see or avoid him as well, and spots
|
||
are soon the "in" thing. This was a beneficial mutation. From the
|
||
same parent stock we soon have two differing sub-species, one striped,
|
||
living on the plains, and one spotted, living in the woods.
|
||
|
||
In a domestic situation, a litter is born to two normal cats, wherein
|
||
one of the kittens is hairless. Thinking the hairlessness is differ-
|
||
ent enough to be a desired feature, especially for those with aller-
|
||
gies, the kitten is very carefully bred to other cats, back and forth
|
||
over several generations, until the hairlessness breeds true. Thus
|
||
the Sphinx, a hairless domestic cat and the ultimate in hypo-allergen-
|
||
ic cats, was developed.
|
||
|
||
The Mapped-out Genes
|
||
|
||
|
||
----------------------------------------------------------------------
|
||
Feline Genetics Page 9
|
||
|
||
|
||
|
||
|
||
|
||
As stated earlier, a few of the common cat genes have been identified
|
||
and mapped. These genes are grouped according to the effects they
|
||
have: the body-conformation genes which affect the shape of the body
|
||
of body parts; the coat-conformation genes which affect the texture
|
||
and length of the coat; and the color-conformation genes which affect
|
||
the color and pattern of the coat.
|
||
|
||
The color-conformations genes are themselves divided into three
|
||
groups: the color genes which control the color of the coat and its
|
||
density; the color-pattern genes which control the pattern of the coat
|
||
and expression of the color; and the color-masking genes which control
|
||
the degree and type of masking of the basic color.
|
||
|
||
The Body-Conformation Genes
|
||
|
||
The body-conformation genes affect the basic conformation of the parts
|
||
of the body: ears, tail and feet. There are literally thousands of
|
||
body conformation genes, but only a few have been mapped: normal or
|
||
Scottish fold ears, normal or Japanese bobtail, normal or Manx tail-
|
||
lessness and spinal curve, and normal or polydactyl feet.
|
||
|
||
The Scottish-fold gene: normal or folded ears. The wild allele,
|
||
"fd", is recessive and produces normal ears. The mutation, "Fd", is
|
||
dominant and produces the cap-like folded ears of the Scottish Fold.
|
||
This mutant gene is crippling when homozygous.
|
||
|
||
The Japanese Bobtail gene: normal or short tail. The wild allele,
|
||
"Jb", is dominant and produces normal-length tails. The mutation,
|
||
"jb", is recessive and produces the short tail of the Japanese Bob-
|
||
tail. Unlike the Manx mutation, this mutation is not crippling and
|
||
does not cause deformation of the spine.
|
||
|
||
The Manx gene: normal or missing tail. The wild allele, "m", is
|
||
recessive and produces normal-length tails and proper spinal conforma-
|
||
tion. The mutation, "M", is dominant and produces the missing tail
|
||
and shortened spine of the Manx. This mutation is lethal when homozy-
|
||
gous. When heterozygous, it is often crippling, sometimes resulting
|
||
in spinal bifida, imperforate anus, chronic constipation, or inconti-
|
||
nence.
|
||
|
||
The polydactyl gene: normal-number or extra toes. The wild allele,
|
||
"pd", is recessive and produces the normal number of toes. The muta-
|
||
tion, "Pd", is dominant and produces extra toes, particularly upon the
|
||
front paws.
|
||
|
||
Interestingly, humans also have a similar dominant polydactyl gene
|
||
controlling the number of fingers. Homozygous people with six fingers
|
||
on each hand will pass that trait on to all their children, heterozy-
|
||
gous people to one in four of their children, even with a normal mate:
|
||
the gene is dominant. Just because a given mutation is dominant,
|
||
however, doesn't mean it will dominate the species. If a given muta-
|
||
tion is not conducive to survival of the individual or inhibits mating
|
||
in any way, it will never become "popular," no matter how dominant it
|
||
|
||
|
||
----------------------------------------------------------------------
|
||
Feline Genetics Page 10
|
||
|
||
|
||
|
||
|
||
may be.
|
||
|
||
The Coat-Conformation Genes
|
||
|
||
The coat conformation genes affect such things as the length and
|
||
texture of the coat.
|
||
|
||
The Sphinx gene: hairy or hairless coat. The wild allele, "Hr", is
|
||
dominant and produces a normal hairy coat. The mutation, "hr", is
|
||
recessive and produces the hairless or nearly hairless coat of the
|
||
Sphinx.
|
||
|
||
The longhaired gene: short or long coat. The wild allele, "L", is
|
||
dominant and produces a normal shorthaired coat. The mutation, "l",
|
||
is recessive and produces the longhaired coat of the Persians, Ango-
|
||
ras, Main Coons, and others.
|
||
|
||
The Cornish Rex gene: straight or curly coat. The wild allele, "R",
|
||
is dominant and produces a normal straighthaired coat. The mutation,
|
||
"r", is recessive and produces the very short curly coat, without
|
||
guard hairs, of the Cornish Rex.
|
||
|
||
The Devon Rex gene: straight or curly coat. The wild allele, "Re",
|
||
is dominant and produces a normal straighthaired coat. The mutation,
|
||
"re", is recessive and produces the very short curly coat of the Devon
|
||
Rex. Unlike the Cornish Rex, the Devon Rex retains guard hairs in its
|
||
coat.
|
||
|
||
The Oregon Rex gene: straight or curly coat. The wild allele, "Ro",
|
||
is dominant and produces a normal straighthaired coat. The mutation,
|
||
"ro", is recessive and produces the very short curly coat of the
|
||
Oregon Rex. Like the Cornish Rex, the Oregon Rex lacks guard hairs.
|
||
|
||
The American Wirehair gene: soft or bristly coat. The wild allele,
|
||
"wh", is recessive and produces a normal soft straighthaired coat.
|
||
The mutation, "Wh", is dominant and produces the short, stiff, wiry
|
||
coat of the American Wirehair.
|
||
|
||
Note that there are three different Rex mutations producing almost
|
||
identical effect. There are still three different genes involved,
|
||
however.
|
||
|
||
The Color-Conformation Genes
|
||
|
||
The color-conformation genes determine the color, pattern, and expres-
|
||
sion of the coat. Since these characteristics are among the most
|
||
important of the cat's features, at least from a breeding point of
|
||
view, more emphasis is given the color conformation genes than the
|
||
others.
|
||
|
||
These genes fall into three logical groups: those that control the
|
||
color, those that control the pattern, and those that control the
|
||
color expression. Each of these groups contains several differing but
|
||
interrelated genes.
|
||
|
||
|
||
----------------------------------------------------------------------
|
||
Feline Genetics Page 11
|
||
|
||
|
||
|
||
|
||
|
||
The Color Gene
|
||
|
||
The first of the genes controlling coat color is the color gene. This
|
||
gene controls the actual color of the coat and comes in three alleles:
|
||
black, dark brown, or light brown. This three-level dominance is not
|
||
at all uncommon: the albinism gene, for example, has five levels.
|
||
|
||
The black allele, "B", is wild, is dominant, and produces a black or
|
||
black-and-brown tabby coat, depending upon the presence of the agouti
|
||
gene. Technically, the black is an almost-black, super-dark brown
|
||
that is virtually black -- true black is theoretically impossible, but
|
||
often reached in the practical sense (so much for theory).
|
||
|
||
The dark-brown allele, "b", is mutant, is recessive to black but
|
||
dominant to light brown, and reduces black to dark brown.
|
||
|
||
The light-brown allele, "bl", is mutant, is recessive to both black
|
||
and dark brown, and reduces black to a medium brown.
|
||
|
||
The Orange-Making Gene
|
||
|
||
The second of the genes controlling coat color is the orange-making
|
||
gene. This gene controls the conversion of the coat color into orange
|
||
and the masking of the agouti gene and comes in two alleles: non-
|
||
orange and orange.
|
||
|
||
The non-orange allele, "o", is wild and allows full expression of the
|
||
black or brown colors. The orange allele, "O", is mutant and converts
|
||
black or brown to orange and masks the effects of the non-agouti
|
||
mutation of the agouti gene (all orange cats are tabbies).
|
||
|
||
This gene is sex-linked -- it is carried on the "X" chromosome beyond
|
||
the limit of the "Y" chromosome. Therefore, in males there is no
|
||
homologous pairing, and the single orange-making gene stands alone.
|
||
As a result there is no dominance effect in males: they are either
|
||
orange or non-orange. If a male possesses the non-orange allele, "o",
|
||
all colors (black, dark brown, or light brown) will be expressed. If
|
||
he possesses the orange allele, "O", all colors will be converted to
|
||
orange.
|
||
|
||
In females there is an homologous pairing, one gene being carried on
|
||
each of the two "X" chromosomes. These two genes act together in a
|
||
very special manner (as a sort of tri-state gene), and again there is
|
||
no dominance effect.
|
||
|
||
If the female is homozygous for non-orange, "oo", all colors will be
|
||
expressed. If she is homozygous for orange, "OO", all colors will be
|
||
converted to orange. It is when she is heterozygous for orange, "Oo",
|
||
that interesting things begin to happen: through a very elegant
|
||
process, the black-and-orange tortoiseshell or brindled female is
|
||
possible.
|
||
|
||
Shortly after conception, when a female zygote is only some dozens of
|
||
|
||
|
||
----------------------------------------------------------------------
|
||
Feline Genetics Page 12
|
||
|
||
|
||
|
||
|
||
cells in size, a chemical trigger is activated to start the process of
|
||
generating a female kitten. This same trigger also causes the zygote
|
||
to "rationalize" all the sex-linked characteristics, including the
|
||
orange-making genes. In this particular case, suppression of one of
|
||
the orange-making genes in each cell takes place in a not-quite-random
|
||
pattern (there is some polygene influence here). Each cell will then
|
||
carry only one orange-making gene.
|
||
|
||
Since the zygote was only some dozens of cells in size at the time of
|
||
rationalization, only a few of those cells will eventually determine
|
||
the color of the coat (the orange-making genes in the other cells will
|
||
be ignored). If the zygote were homozygous for non-orange, "oo", then
|
||
all cells will contain "o", and the coat will be non-orange. Like-
|
||
wise, if the zygote were homozygous for orange, "OO", then all cells
|
||
will contain "O", and the coat will be orange. If, however, the
|
||
zygote were heterozygous, "Oo", then some of the cells will contain
|
||
"O" and the rest of the cells will contain "o". In this case, those
|
||
portions of the coat determined by "O" cells will be orange, while
|
||
those portions determined by "o" cells will be non-orange. Voila! A
|
||
tortoiseshell cat!
|
||
|
||
A female kitten has two "X" chromosomes, and therefore two orange-
|
||
making genes, one from each parent. Assuming for the sake of discus-
|
||
sion an equal likelihood of inheriting either allele from each parent
|
||
-- an assumption that is patently false, but used here for demonstra-
|
||
tion only -- then one quarter of all females would be non-orange, one-
|
||
quarter would be orange, and one-half would be tortoiseshell. A male
|
||
kitten, on the other hand, has only one "X" chromosome, and therefore
|
||
only one orange-making gene. Keeping the same false assumption of
|
||
equal likelihood, then one-half of all males would be non-orange and
|
||
one-half would be orange. This means that there would be twice as
|
||
many orange males as females if our assumption were correct.
|
||
|
||
Our equal-likelihood assumption is not correct, however. The orange-
|
||
making gene is located adjacent to the centromere and is often damaged
|
||
during meiosis. This damage tends to make an orange allele into a
|
||
non-orange allele, giving the non-orange allele a definite leg up, so
|
||
to speak, in a 7:3 ratio. This means that among female kittens 49%
|
||
will be non-orange, 42% will be tortoiseshell, and only 9% will be
|
||
orange, while among male kittens 70% will be non-orange and 30% will
|
||
be orange: there will be more than 3 times as many orange males as
|
||
females. That's why there are so many Morris-type males around.
|
||
|
||
Since a male has only one orange-making gene, there cannot be a male
|
||
tortie. An exception to this rule is the hermaphrodite, which has an
|
||
"XXY" genetic structure. Such a cat can be tortie, since it has two
|
||
"X" chromosomes, but must invariably be sterile. In fact, despite the
|
||
presence of male genitalia, a hermaphrodite is genetically an underde-
|
||
veloped female, and may have both ovaries and testes, with neither
|
||
fully functional.
|
||
|
||
The Color-Density Gene
|
||
|
||
The third and last of the genes controlling the coat color is the
|
||
|
||
|
||
----------------------------------------------------------------------
|
||
Feline Genetics Page 13
|
||
|
||
|
||
|
||
|
||
color-density gene. This gene controls the uniformity of distribution
|
||
of pigment throughout the hair and comes in two alleles: dense, "D",
|
||
and dilute, "d".
|
||
|
||
The dense allele, "D", is wild, is dominant, and causes pigment to be
|
||
distributed evenly throughout each hair, making the color deep and
|
||
pure. A dense coat will be black, dark brown, medium brown, or or-
|
||
ange.
|
||
|
||
The dilute allele, "d", is mutant, is recessive, and causes pigment to
|
||
be agglutinated into microscopic clumps surrounded by translucent
|
||
unpigmented areas, allowing white light to shine through and diluting
|
||
the color. A dilute coat will be blue (gray), tan, beige, or cream.
|
||
|
||
The Eight Cat Colors
|
||
|
||
All possible expressions of the color, orange-making, and color-
|
||
density genes produce the eight basic coat colors: black, blue
|
||
(gray), chestnut or chocolate (dark-brown), lavender or lilac (tan),
|
||
cinnamon (medium brown), fawn (beige), red (orange), and cream.
|
||
|
||
| Sex | "BB Bb Bbl bb bbl blbl"
|
||
-----+--------+-------------------------------------------------------
|
||
ooDD | Either | Black Black Black Chestnut Chestnut Cinna
|
||
-----+--------+-------------------------------------------------------
|
||
ooDd | Either | Black Black Black Chestnut Chestnut Cinna
|
||
-----+--------+-------------------------------------------------------
|
||
oodd | Either | Blue Blue Blue Lavender Lavender Fawn
|
||
-----+--------+-------------------------------------------------------
|
||
oODD | Female | Blk/Red Blk/Red Blk/Red Chs/Red Chs/Red Cin/Red
|
||
| Male | Black Black Black Chestnut Chestnut Cinna
|
||
-----+--------+-------------------------------------------------------
|
||
oODd | Female | Blk/Red Blk/Red Blk/Red Chs/Red Chs/Red Cin/Red
|
||
| Male | Black Black Black Chestnut Chestnut Cinna
|
||
-----+--------+-------------------------------------------------------
|
||
oOdd | Female | Blu/Crm Blu/Crm Blu/Crm Lav/Crm Lav/Crm Fwn/Crm
|
||
| Male | Blue Blue Blue Lavender Lavender Fawn
|
||
-----+--------+-------------------------------------------------------
|
||
OoDD | Female | Blk/Red Blk/Red Blk/Red Chs/Red Chs/Red Cin/Red
|
||
| Male | Red Red Red Red Red Red
|
||
-----+--------+-------------------------------------------------------
|
||
OoDd | Female | Blk/Red Blk/Red Blk/Red Chs/Red Chs/Red Cin/Red
|
||
| Male | Red Red Red Red Red Red
|
||
-----+--------+-------------------------------------------------------
|
||
Oodd | Female | Blu/Crm Blu/Crm Blu/Crm Lav/Crm Lav/Crm Fwn/Crm
|
||
| Male | Cream Cream Cream Cream Cream Cream
|
||
-----+--------+-------------------------------------------------------
|
||
OODD | Either | Red Red Red Red Red Red
|
||
-----+--------+-------------------------------------------------------
|
||
OODd | Either | Red Red Red Red Red Red
|
||
-----+--------+-------------------------------------------------------
|
||
OOdd | Either | Cream Cream Cream Cream Cream Cream
|
||
|
||
The brown and dilute colors are rarer (hence generally more prized)
|
||
|
||
|
||
----------------------------------------------------------------------
|
||
Feline Genetics Page 14
|
||
|
||
|
||
|
||
|
||
because they are recessive. A table of all possible combinations of
|
||
the three genes controlling color will show all eight basic coat
|
||
colors, among which are six female or twelve male black cats but only
|
||
one female or two male fawn:
|
||
|
||
Note that although tortoiseshell females are two-color they introduce
|
||
no new colors.
|
||
|
||
It may also be noted that red and cream dominate any of the true
|
||
(black or brown) colors: a red coat is red regardless of whether the
|
||
color gene is black, dark brown, or light brown. The color gene is
|
||
masked by the orange-making gene. This, coupled with the fact that
|
||
males are either red or non-red require that the color chart show "oO"
|
||
and "Oo" as distinctly separate. A male has only the first of the two
|
||
genes: "o" from "oO" or "O" from "Oo". In some texts, the orange-
|
||
making genes are indicated as "o(O)" and "O(o)" to emphasize the
|
||
sexual distinction.
|
||
|
||
The Albinism Gene
|
||
|
||
The first of the color-conformation genes affect coat pattern is the
|
||
albinism gene. This gene controls the amount of body color and comes
|
||
in five alleles: full color, "C", Burmese, "cb", Siamese, "cs", blue-
|
||
eyed albino, "ca", and albino, "c".
|
||
|
||
The full color allele, "C" is wild, is dominant, and produces a full
|
||
expression of the coat colors. This is sometimes called the non-
|
||
albino allele.
|
||
|
||
The Burmese allele, "cb", is mutant, is recessive to the full color
|
||
allele, codominant with the Siamese allele, and dominant to the blue-
|
||
eyed albino and albino alleles, and produces a slight albinism, reduc-
|
||
ing black to a very dark brown, called sable in the Burmese breed, and
|
||
producing green or green-gold eyes.
|
||
|
||
The Siamese allele, "cs", is mutant, is recessive to the full color
|
||
allele, codominant with the Siamese allele, and dominant to the blue-
|
||
eyed albino and albino alleles, and produces an intermediate albinism,
|
||
reducing the basic coat color from black/brown to a light beige with
|
||
dark brown "points" in the classic Siamese pattern and producing
|
||
bright blue eyes.
|
||
|
||
The Burmese and Siamese alleles are codominant, that is they each have
|
||
exactly as much dominance or recessivity. It is possible to have one
|
||
of each allele, "cbcs", producing a Siamese-patterned coat with a
|
||
darker base body color and turquoise (aquamarine) eyes: the Tonkinese
|
||
pattern.
|
||
|
||
The blue-eyed albino allele, "ca", is mutant, is recessive to the full
|
||
color, Burmese and Siamese alleles and dominant to the albino allele,
|
||
and produces a nearly complete albinism with a translucent white coat
|
||
and very washed-out pale blue eyes.
|
||
|
||
The albino allele, "c", is mutant, is recessive to all others, and
|
||
|
||
|
||
----------------------------------------------------------------------
|
||
Feline Genetics Page 15
|
||
|
||
|
||
|
||
|
||
produces a complete albinism with a translucent white coat and pink
|
||
eyes.
|
||
|
||
The albanism genes combine in some rather interesting ways:
|
||
|
||
| C cb cs ca c
|
||
---+-----------------------------------------------------------
|
||
C | full color full color full color full color full color
|
||
cb | full color Burmese Tonkinese Burmese Burmese
|
||
cs | full color Tonkinese Siamese Siamese Siamese
|
||
ca | full color Burmese Siamese B-E Albino B-E Albino
|
||
c | full color Burmese Siamese B-E Albino Albino
|
||
|
||
Notice how the dominance characteristics among the alleles are normal
|
||
except for the combination of Burmese and Siamese, which produce the
|
||
Tonikinese pattern.
|
||
|
||
The Agouti Gene
|
||
|
||
The next gene controlling the pattern of the coat is the agouti gene.
|
||
This gene will control ticking and comes in two alleles: agouti, "A",
|
||
and non-agouti, "a".
|
||
|
||
The agouti allele, "A", is wild, is dominant, and produces a banded
|
||
or ticked (agouti) hair, which in turn will produce a tabby coat
|
||
pattern.
|
||
|
||
The non-agouti allele, "a", is mutant, is recessive, and suppresses
|
||
ticking, which in turn will produce a solid-color coat. This gene
|
||
only operates upon the color gene (black, dark brown, or light brown)
|
||
in conjunction with the non-orange allele of the orange-making gene
|
||
and is masked by the orange allele of the orange-making gene.
|
||
|
||
The Tabby Genes
|
||
|
||
The last of the genes affecting the coat pattern is the tabby gene.
|
||
This gene will control the actual coat pattern (striped, spotted,
|
||
solid, etc.) and comes in three alleles: mackerel or striped tabby,
|
||
"T", Abyssinian or all-agouti-tabby, "Ta", and blotched or classic
|
||
tabby, "tb".
|
||
|
||
The mackerel-tabby allele, "T", is wild, is co-dominant with the
|
||
spotted tabby and Abyssinian alleles and dominant to the classic-tabby
|
||
allele, and produces a striped cat, with vertical non-agouti stripes
|
||
on an agouti background. This is the most common of all patterns and
|
||
is typical grassland camouflage, where shadows are long and strait.
|
||
|
||
A spotted tabby is genetically a striped tabby with the stripes broken
|
||
up by polygene influence. There is no specific "spotted-tabby" gene.
|
||
This spotted coat is a typical forest camouflage, where shadows are
|
||
dappled by sunlight shining through the trees. Do not confuse the
|
||
spots of our domestic cats with the rosettes of the true spotted cats:
|
||
entirely different genes are involved.
|
||
|
||
|
||
|
||
----------------------------------------------------------------------
|
||
Feline Genetics Page 16
|
||
|
||
|
||
|
||
|
||
The Abyssinian allele, "Ta", is mutant, is codominant to the mackerel-
|
||
tabby allele and dominant to the classic-tabby allele, and will pro-
|
||
duce an all-agouti coat without stripes or spots. This all-agouti
|
||
coat is a basic type of bare-ground camouflage, seen in the wild
|
||
rabbit and many other animals.
|
||
|
||
A special case occurs when both the mackerel-tabby and Abyssinian
|
||
alleles are expressed, "TTa". This will produce a unique coat con-
|
||
sisting of the beige ground color with each hair tipped with the
|
||
expressed color. By selective breeding, the ground color has become a
|
||
soft gold, producing the beautiful golden chinchilla cats.
|
||
|
||
The blotched- or classic-tabby allele, "tb", is recessive to both the
|
||
mackerel-tabby and the Abyssinian alleles and will produce irregular
|
||
non-agouti blotches or "cinnamon-roll" sworls on an agouti background.
|
||
When the "cinnamon-rolls" are clean and symmetrical, and nicely cen-
|
||
tered on the sides, a strikingly beautiful coat is achieved.
|
||
|
||
The "coat of choice" in Europe is the classic tabby (hence the name),
|
||
probably because of the similarity in appearance of a large mackerel
|
||
tabby domestic cat and the European Wildcat, the former being soft and
|
||
cuddly and the latter prone to remove fingers. In the U.S., the
|
||
reverse is true.
|
||
|
||
The Color-Inhibitor Gene
|
||
|
||
The first of the color-conformation genes controlling color expression
|
||
is the color-inhibitor gene. This gene controls the expression of
|
||
color within the hair and comes in two alleles: the non-inhibitor,
|
||
"i", and the inhibitor, "Y".
|
||
|
||
The non-inhibitor allele, "i", is wild, is recessive, and allows
|
||
expression of the color throughout the length of the hair, producing a
|
||
normally colored coat.
|
||
|
||
The inhibitor allele, "I", is mutant, is dominant, and inhibits ex-
|
||
pression of the color over a portion of the hair.
|
||
|
||
The inhibitor allele is variably-expressed. When slightly expressed,
|
||
the short down hairs (underfur) are merely tipped with color, while
|
||
the longer guard and awn hairs are clear for about the first quarter
|
||
of their lengths: the coat is said to be smoked. When moderately
|
||
expressed, the down hairs are completely clear and the longer hairs
|
||
are clear for about half their lengths: the coat is shaded. When
|
||
heavily expressed, the down hairs are completely clear and the longer
|
||
hairs are clear for about three-quarters (or more) of their lengths:
|
||
the coat is then tipped or chinchilla.
|
||
|
||
Neither allele has anything to do with the actual color or pattern,
|
||
only with whether that color is laid upon a clear undercoat or one of
|
||
the beige ground color.
|
||
|
||
The Spotting Gene
|
||
|
||
|
||
|
||
----------------------------------------------------------------------
|
||
Feline Genetics Page 17
|
||
|
||
|
||
|
||
|
||
The next gene controlling color expression is the white-spotting gene.
|
||
This gene controls the presence and pattern of white masking the
|
||
normal coat pattern, and has four alleles: non-spotted, "s", spotted,
|
||
"S", particolor, "Sp", and Birman, "sb". The presence of the parti-
|
||
color and Birman alleles of this gene are still subject to argument at
|
||
this time: their effect is not.The non-spotted allele, "s", is wild,
|
||
is recessive, and produces a normal coat without white.
|
||
|
||
The spotted allele, "S", is mutant, is dominant, and produces white
|
||
spotting which masks the true coat color in the affected area. This
|
||
is a variably-expressed allele with a very wide expression range:
|
||
From a black cat with one white hair to a white cat with one black
|
||
hair.
|
||
|
||
The particolor allele, "Sp", if it exists, is a variation of the
|
||
spotted allele affecting the pattern of white. The classic particolor
|
||
pattern is an inverted white "V" starting in the center of the fore-
|
||
head and passing through the centers of the eyes. The chin, chest,
|
||
belly, legs and feet are white. Variable expressions of this allele
|
||
range downward to a simple white locket or a white spot on the fore-
|
||
head.
|
||
|
||
The Birman allele, "Sb", if it exists, is a variation of the spotted
|
||
allele producing white feet. Variable expression ranges from white
|
||
legs and feet to white toes only.
|
||
|
||
Unlike the white gene or the albinism gene, the white-spotting gene
|
||
does not affect eye color: if your all white cat has green eyes, it
|
||
is most definitely a colored cat with one big white spot all over.
|
||
|
||
The Dominant-White Gene
|
||
|
||
The final gene controlling color expression is the dominant-white
|
||
gene. This gene determines whether the coat is solid white or not,
|
||
and comes in three alleles: non-white, "w", white, "W", and van,
|
||
"Wv". The existence of the van allele is open to argument: it may be
|
||
a separate gene.
|
||
|
||
The non-white allele, "w", is wild, is recessive, and allows full
|
||
expression of the coat color and pattern.
|
||
|
||
The white allele, "W", is mutant, is dominant, and produces a translu-
|
||
cent all-white coat with either orange or pale blue. Blue-eyed domi-
|
||
nant-white cats are often deaf, orange-eyed cats occasionally so.
|
||
Interestingly, a white cat may be odd-eyed, having one blue and one
|
||
orange eye. Such a cat is often deaf on the blue side.
|
||
|
||
The van allele, "Wv", if it exists, is a variation of the white allele
|
||
allowing color in the classic van pattern: on the crown of the head
|
||
(often a two small half-caps separated by a thin white line), on the
|
||
ears, and on the tail. Variable expression controls cap size and
|
||
shape and the presence of color on the ears and tail. Occasionally,
|
||
the caps will be missing and only the ears and/or tail will be col-
|
||
ored.
|
||
|
||
|
||
----------------------------------------------------------------------
|
||
Feline Genetics Page 18
|
||
|
||
|
||
|
||
|
||
|
||
It is important to remember that, genetically speaking, white is not a
|
||
color, but rather the suppression of the pigment that would normally
|
||
be present. A heterozygous white cat can an often does produce col-
|
||
ored kittens, sometimes with no white at all.
|
||
|
||
Polygenes
|
||
|
||
The genes described above control color and coat, and several breed-
|
||
specific body features, but what about the genes that control the body
|
||
structure itself? Can we not develop a cat with long floppy ears
|
||
(sort of a bassett-cat)? The answer is a qualified no. Not within
|
||
the realms of normal breeding, and not without a much better means of
|
||
genetic engineering than is currently available to us. The reason
|
||
cats (and horses) resist major changes, whereas dogs do not, is be-
|
||
cause the genes controlling these features are scattered among the
|
||
genetic codes of other genes (remember, a gene is not a physical
|
||
entity but rather a series of instructions). This type of scattered
|
||
gene is called a "polygene". Polygenes are in firm control of many of
|
||
those things that define the cat, and breeding programs can only
|
||
change these characteristics slowly, bit-by-bit.
|
||
|
||
The Eye Colors
|
||
|
||
There are no specific genes for the eye colors. Rather, the color of
|
||
the eyes is intimately linked to the color and pattern of the coat via
|
||
several polygenes.
|
||
|
||
There is much about eye color that is not yet understood. As an
|
||
example, the British Blue usually has orange or copper eyes while
|
||
those of the Russian Blue are usually green, in spite of the fact that
|
||
the breeds have identical coat genotypes.
|
||
|
||
The range of eye color is from a deep copper-orange through yellow to
|
||
green. The blue and pink eyed cats are partial or full albinos, with
|
||
suppression of the eye color.
|
||
|
||
Color Abr Description
|
||
-------------------------------------------------------------
|
||
Copper cpr Deep copper-orange
|
||
Orange org Bright orange
|
||
Amber amb Yellow-orange
|
||
Yellow yel Yellow
|
||
Gold gld Dark yellow with hint of green
|
||
Hazel hzl Dark greenish-yellow
|
||
Green grn Green
|
||
Turquoise trq Bluish-green (common in Tonkinese)
|
||
Siamese Blue sbl Royal Blue to medium-pale grayish-blue
|
||
Dominant-White Blue wbl Medium blue
|
||
Dominant-White Odd odd One blue, one orange
|
||
Albino Blue abl Very pale blue, almost gray
|
||
Albino Pink pnk Pink
|
||
|
||
There is a definite interaction between the color genes, "B", "b", and
|
||
|
||
|
||
----------------------------------------------------------------------
|
||
Feline Genetics Page 19
|
||
|
||
|
||
|
||
|
||
"bl", the color density genes, "D" and "d", and eye color. This
|
||
interaction is especially evident in those cats with Siamese coats
|
||
where the eye color can range from a strikingly deep, rich blue for a
|
||
Seal Point coat to a medium-pale, grayish blue for a lilac point coat.
|
||
|
||
Naming the Colors
|
||
|
||
When it came to naming the colors, those who did so were firm believ-
|
||
ers in using the thesaurus: never call a color brown when you can
|
||
call it chocolate or cinnamon.
|
||
|
||
The colors naturally fall into distinct groups: the "standard" col-
|
||
ors, the shaded colors, the "exotic" colors, the oriental colors, and
|
||
the whites. Each group may then be subdivided into several distinct
|
||
smaller groups, each with a common characteristic. Each color name is
|
||
followed by its karyotype in three groups (as they were discussed
|
||
above), and the usual eye colors. Bear in mind that all possible
|
||
combinations of color and pattern will eventually be realized, but not
|
||
necessarily recognized: especially by the various cat fancies.
|
||
|
||
The Standard Solid Colors
|
||
|
||
The solids form the basis for all other colors in nomenclature and
|
||
karyotypes: these are the fundamental rendition of the eight basic
|
||
coat colors. Solids are called "selfs" in Britain.
|
||
|
||
The black solid technically has a brown undercoat, but selective
|
||
breeding has managed to eliminate the brown undercoat and has produced
|
||
cats that are "black to the bone."
|
||
|
||
The subtle differences possible in blues (grays) has made this one of
|
||
the most popular colors among breeders, with several breeds being
|
||
exclusively blue. Blues, regardless of pattern, are often referred to
|
||
as "dilutes."
|
||
|
||
The terms "chestnut" and "chocolate" are synonymous, as are the terms
|
||
"lavender" and "lilac."
|
||
|
||
Since the orange allele of the orange-making gene also masks the non-
|
||
agouti allele of the agouti gene, red and cream solids are genetically
|
||
identical to red and cream tabbies. Careful selective breeding has
|
||
made cause the non-agouti areas (the stripes) to widen and overlap,
|
||
effectively canceling the paler agouti background and obscuring the
|
||
tabby pattern. A generation or two of random breeding, however, and
|
||
the stripes will return.
|
||
|
||
The patched solids, solid-and-whites or bi-colors, are formed by
|
||
adding the white-spotting gene, "S*", to the solids. If, instead of
|
||
the normal random white spotting gene, the particolor gene, "Sp*", is
|
||
present, then the coat will show white in the particolor pattern. If
|
||
both the random white-spotting and particolor genes, "SSp", are
|
||
present, then a composite pattern will be evident. If the Birman
|
||
gene, "sbsb", is present, then the pattern will be white feet only.
|
||
|
||
|
||
|
||
----------------------------------------------------------------------
|
||
Feline Genetics Page 20
|
||
|
||
|
||
|
||
|
||
The tortoiseshells or torties are formed by combining both the domi-
|
||
nant and recessive sex-linked orange genes, "Oo", with the solids.
|
||
Because of the sex-linking of the orange genes, the tortie is always
|
||
female. A tabby pattern may be visible in the orange areas, with any
|
||
tabby pattern being permitted. In some individuals, the agouti and
|
||
non-agouti orange areas may offer such contrast as to produce a false
|
||
tri-color (black-orange-cream).
|
||
|
||
The patched tortoiseshells or calicos are formed by combining both the
|
||
dominant and recessive sex-linked orange-making genes, "Oo", to the
|
||
solids and adding the white-spotting gene, "S*". Like the torties,
|
||
the calicos are always female, and like the patches, any white-
|
||
spotting pattern is permitted.
|
||
|
||
Color | Karyotype | Usual eye color
|
||
---------------------+--------------------------+----------------
|
||
Black | B*ooD* C*aa** iissww | cpr org grn
|
||
Blue | B*oodd C*aa** iissww | cpr org grn
|
||
Chestnut | b*ooD* C*aa** iissww | cpr org
|
||
Lavender | b*oodd C*aa** iissww | cpr org gld
|
||
Cinnamon | blblooD* C*aa** iissww | org
|
||
Fawn | blbloodd C*aa** iissww | org gld
|
||
Red | **OOD* C***T* iissww | cpr org
|
||
Cream | **OOdd C***T* iissww | cpr org
|
||
---------------------+--------------------------+----------------
|
||
Black patch | B*ooD* C*aa** iiS*ww | cpr org grn
|
||
blue patch | B*oodd C*aa** iiS*ww | cpr org grn
|
||
chestnut patch | b*ooD* C*aa** iiS*ww | cpr org
|
||
lavender patch | b*oodd C*aa** iiS*ww | cpr org grn
|
||
cinnamon patch | blblooD* C*aa** iiS*ww | org
|
||
fawn patch | blbloodd C*aa** iiS*ww | org grn
|
||
red patch | **OOD* C***T* iiS*ww | cpr org
|
||
cream patch | **OOdd C***T* iiS*ww | cpr org
|
||
|
||
The Standard Tabby Colors
|
||
|
||
The tabbies are formed by adding the agouti gene, "A*", to the solids.
|
||
This causes the otherwise solid color to show the pattern dictated by
|
||
the tabby gene: light and dark stripes (mackerel allele, "T*") or
|
||
blotches (blotched allele, "tbtb").
|
||
|
||
The brown tabby corresponds to the black solid: sufficient undercoat
|
||
color shows in the agouti areas to provide a brownish cast. When in
|
||
mackerel pattern, this is the "all wild" genotype, and represents the
|
||
natural state of the cat.
|
||
|
||
The red tabby, when in mackerel pattern, presents an alternate stable
|
||
coat often found on feral domestic cats, usually as a pale ginger.
|
||
|
||
The patched tabbies or tabby-and-whites are formed by adding the white
|
||
spotting gene, "S*", to the tabbies. Like the patched solids, any
|
||
white spotting pattern is permitted.
|
||
|
||
The tabby-tortoiseshells or torbies are formed by combining both the
|
||
|
||
|
||
----------------------------------------------------------------------
|
||
Feline Genetics Page 21
|
||
|
||
|
||
|
||
|
||
dominant and recessive sex-linked orange genes, "Oo", with the tabbies
|
||
colors. Like the torties, the torbies are always female.
|
||
|
||
Color | Karyotype | Usual eye color
|
||
-----------------------+-------------------------+----------------
|
||
tortie | B*OoD* C*aaT* iissww | cpr org
|
||
blue tortie | B*Oodd C*aaT* iissww | cpr org grn
|
||
chestnut tortie | b*OoD* C*aaT* iissww | cpr org
|
||
lavender tortie | b*Oodd C*aaT* iissww | cpr org grn
|
||
cinnamon tortie | blblOoD* C*aaT* iissww | org
|
||
fawn tortie | blblOodd C*aaT* iissww | org grn
|
||
-----------------------+-------------------------+----------------
|
||
calico | B*OoD* C*aaT* iiS*ww | cpr org
|
||
blue calico | B*Oodd C*aaT* iiS*ww | cpr org grn
|
||
chestnut calico | b*OoD* C*aaT* iiS*ww | cpr org
|
||
lavender calico | b*Oodd C*aaT* iiS*ww | cpr org grn
|
||
cinnamon calico | blblOoD* C*aaT* iiS*ww | org
|
||
fawn calico | blblOodd C*aaT* iiS*ww | org grn
|
||
-----------------------+-------------------------+----------------
|
||
brown tabby | B*ooD* C*A*T* iissww | cpr org yel hzl
|
||
blue tabby | B*oodd C*A*T* iissww | cpr org yel hzl
|
||
chestnut tabby | b*ooD* C*A*T* iissww | cpr org yel hzl
|
||
lavender tabby | b*oodd C*A*T* iissww | cpr org yel hzl
|
||
cinnamon tabby | blblooD* C*A*T* iissww | org yel hzl
|
||
fawn tabby | blbloodd C*A*T* iissww | org yel hzl
|
||
red tabby | **OOD* C***T* iissww | cpr org yel hzl
|
||
cream tabby | **OOdd C***T* iissww | cpr org yel hzl
|
||
-----------------------+-------------------------+----------------
|
||
brown patched tabby | B*ooD* C*A*T* iiS*ww | cpr org yel hzl
|
||
blue patched tabby | B*oodd C*A*T* iiS*ww | cpr org yel hzl
|
||
chestnut patched tabby | b*ooD* C*A*T* iiS*ww | cpr org yel hzl
|
||
lavender patched tabby | b*oodd C*A*T* iiS*ww | cpr org yel hzl
|
||
cinnamon patched tabby | blblooD* C*A*T* iiS*ww | org yel hzl
|
||
fawn patched tabby | blbloodd C*A*T* iiS*ww | org yel hzl
|
||
red patched tabby | **OOD* C***T* iiS*ww | cpr org yel hzl
|
||
cream patched tabby | **OOdd C***T* iiS*ww | cpr org yel hzl
|
||
-----------------------+-------------------------+----------------
|
||
torbie | B*OoD* C*A*T* iissww | cpr org yel hzl
|
||
blue torbie | B*Oodd C*A*T* iissww | cpr org yel hzl
|
||
chestnut torbie | b*OoD* C*A*T* iissww | cpr org yel hzl
|
||
lavender torbie | b*Oodd C*A*T* iissww | cpr org yel hzl
|
||
cinnamon torbie | blblOoD* C*A*T* iissww | org yel hzl
|
||
fawn torbie | blblOodd C*A*T* iissww | org yel hzl
|
||
-----------------------+-------------------------+----------------
|
||
torbico | B*OoD* C*A*T* iiS*ww | cpr org yel hzl
|
||
blue torbico | B*Oodd C*A*T* iiS*ww | cpr org yel hzl
|
||
chestnut torbico | b*OoD* C*A*T* iiS*ww | cpr org yel hzl
|
||
lavender torbico | b*Oodd C*A*T* iiS*ww | cpr org yel hzl
|
||
cinnamon torbico | blblOoD* C*A*T* iiS*ww | org yel hzl
|
||
fawn torbico | blblOodd C*A*T* iiS*ww | org yel hzl
|
||
|
||
The patched tabby-tortoiseshells, or patched torbies or torbicos, are
|
||
formed by combining the dominant and recessive orange-making genes,
|
||
"Oo", with the standard tabbies and adding the white spotting gene,
|
||
|
||
|
||
----------------------------------------------------------------------
|
||
Feline Genetics Page 22
|
||
|
||
|
||
|
||
|
||
"S*", to the torbie colors. Like the patched solids, any white-
|
||
spotting pattern is permitted.
|
||
|
||
The Shaded Colors
|
||
|
||
The shaded colors are formed by adding the inhibitor gene, "I*", to
|
||
the standard solids. If the expression is light, a smoked coat is
|
||
produced, if moderate, a shaded coat, and if heavy, a tipped or chin-
|
||
chilla coat. Only six of the eight possible colors are recognized.
|
||
|
||
The tortie chinchillas are formed by adding a moderate-to heavy ex-
|
||
pression of the inhibitor gene, "I*", to the standard torties. Only
|
||
four of the six possible colors are recognized.
|
||
|
||
Color | Karyotype | Usual eye color
|
||
-----------------------+-------------------------+----------------
|
||
(silver) smoke | B*ooD* C*aa** I*ssww | cpr org yel
|
||
blue smoke | B*oodd C*aa** I*ssww | cpr org yel
|
||
chestnut smoke | b*ooD* C*aa** I*ssww | cpr org yel
|
||
lavender smoke | b*oodd C*aa** I*ssww | cpr org yel
|
||
red smoke | **OOD* C***T* I*ssww | cpr org yel
|
||
cream smoke | **OOdd C***T* I*ssww | cpr org yel
|
||
-----------------------+-------------------------+----------------
|
||
(silver) shade | B*ooD* C*aa** I*ssww | cpr grn
|
||
blue shade | B*oodd C*aa** I*ssww | cpr grn
|
||
chestnut shade | b*ooD* C*aa** I*ssww | cpr grn
|
||
lavender shade | b*oodd C*aa** I*ssww | cpr grn
|
||
red shade | **OOD* C***T* I*ssww | cpr grn
|
||
cream shade | **OOdd C***T* I*ssww | cpr grn
|
||
-----------------------+-------------------------+----------------
|
||
(silver) chinchilla | B*ooD* C*aa** I*ssww | grn
|
||
blue chinchilla | B*oodd C*aa** I*ssww | grn
|
||
chestnut chinchilla | b*ooD* C*aa** I*ssww | grn
|
||
lavender chinchilla | b*oodd C*aa** I*ssww | grn
|
||
red chinchilla | **OOD* C***T* I*ssww | grn
|
||
cream chinchilla | **OOdd C***T* I*ssww | grn
|
||
-----------------------+-------------------------+----------------
|
||
tortie chinchilla | B*OoD* C*aaT* I*ssww | cpr org yel
|
||
blue tortie chinchilla | B*Oodd C*aaT* I*ssww | cpr org yel
|
||
chestnut tortie chinch | b*OoD* C*aaT* I*ssww | cpr org yel
|
||
lavender tortie chinch | b*Oodd C*aaT* I*ssww | cpr org yel
|
||
|
||
The Golden Chinchilla Colors
|
||
|
||
The golden chinchillas are formed by combining the mackerel and Abys-
|
||
sinian alleles of the tabby gene, "TTa", with the standard solids.
|
||
This produces a coat of undercoat-colored hairs tipped with the stand-
|
||
ard colors. Selective breeding has altered the undercoat polygenes to
|
||
produce a striking warm-gold color. Only three of the eight possible
|
||
colors are recognized.
|
||
|
||
The golden chinchilla torties are formed by combining the mackerel and
|
||
Abyssinian alleles of the tabby gene, "TTa", with the standard
|
||
torties. This produces a coat with hairs of undercoat color tipped
|
||
|
||
|
||
----------------------------------------------------------------------
|
||
Feline Genetics Page 23
|
||
|
||
|
||
|
||
|
||
with the standard tortie colors. While any combination is possible,
|
||
only two colors are recognized.
|
||
|
||
Color | Karyotype | Usual eye color
|
||
-----------------------+-------------------------+----------------
|
||
golden chinchilla | B*ooD* C*A*TTa iissww | gld
|
||
honey chinchilla | b*ooD* C*A*TTa iissww | gld
|
||
copper chinchilla | **OOD* C***TTa iissww | cpr gld
|
||
-----------------------+-------------------------+----------------
|
||
golden tortie chinch | B*OoD* C*A*TTa iissww | gld
|
||
honey tortie chinch | b*OoD* C*A*TTa iissww | gld
|
||
|
||
The Silver Tabby Colors
|
||
|
||
The silver tabbies are obtained by adding a moderate expression of the
|
||
inhibitor gene, I*, to the standard tabbies. Only six of the eight
|
||
possible colors are recognized.
|
||
|
||
Color | Karyotype | Usual eye color
|
||
-----------------------+-------------------------+----------------
|
||
silver tabby | B*ooD* C*A*T* I*ssww | hzl grn
|
||
silver blue tabby | B*oodd C*A*T* I*ssww | hzl grn
|
||
silver chestnut tabby | b*ooD* C*A*T* I*ssww | hzl grn
|
||
silver lilac tabby | b*oodd C*A*T* I*ssww | hzl grn
|
||
silver red tabby | **OOD* C***T* I*ssww | hzl grn
|
||
silver cream tabby | **OOdd C***T* I*ssww | hzl grn
|
||
|
||
The Spotted Tabby Colors
|
||
|
||
The bronze spotted tabbies are genetically standard mackerel tabbies
|
||
with the mackerel striping broken into spots by the effects of various
|
||
polygenes. Ideal coats have evenly spaced round spots. Only six of
|
||
the eight possible colors are recognized.
|
||
|
||
The silver spotted tabbies are bronze spotted tabbies with a moderate
|
||
expression of the inhibitor gene, "I*", added. This produces a pat-
|
||
tern of jet black spots on a silvery agouti background. Only six of
|
||
the eight possible colors are recognized.
|
||
|
||
Color | Karyotype | Usual eye color
|
||
-----------------------+-------------------------+----------------
|
||
bronze | B*ooD* C*A*T* iissww | gld
|
||
bronze blue | B*oodd C*A*T* iissww | cpr gld
|
||
bronze chocolate | b*ooD* C*A*T* iissww | cpr gld
|
||
bronze lavender | b*oodd C*A*T* iissww | cpr gld
|
||
copper | **OOD* C***T* iissww | cop
|
||
bronze cream | **OOdd C***T* iissww | gld
|
||
-----------------------+-------------------------+----------------
|
||
silver | B*ooD* C*A*T* I*ssww | hzl grn
|
||
silver blue | B*oodd C*A*T* I*ssww | hzl grn
|
||
silver chocolate | b*ooD* C*A*T* I*ssww | hzl grn
|
||
silver lilac | b*oodd C*A*T* I*ssww | hzl grn
|
||
silver red | **OOD* C***T* I*ssww | org hzl grn
|
||
silver cream | **OOdd C***T* I*ssww | org hzl grn
|
||
|
||
|
||
----------------------------------------------------------------------
|
||
Feline Genetics Page 24
|
||
|
||
|
||
|
||
|
||
|
||
The Abyssinian Colors
|
||
|
||
The Abyssinians are primarily standard tabbies with the Abyssinian
|
||
allele of the tabby gene, "Ta*". This produces an all-agouti coat,
|
||
similar to that of the wild rabbit.
|
||
|
||
The silver Abyssinians are Abyssinians with a moderate expression of
|
||
the inhibitor gene, "I*". This produces the all-agouti ticking on a
|
||
pale silver undercolor.
|
||
|
||
It should be noted that among Abyssinians there are two genetically
|
||
different reds that are virtually identical in appearance: "red,"
|
||
which is in reality cinnamon, and "true red," which is red.
|
||
|
||
Color | Karyotype | Usual eye color
|
||
-----------------------+-------------------------+----------------
|
||
ruddy | B*ooD* C*A*Ta* iissww | org amb grn
|
||
blue | B*oodd C*A*Ta* iissww | org amb grn
|
||
chestnut | b*ooD* C*A*Ta* iissww | org amb grn
|
||
lavender | b*oodd C*A*Ta* iissww | org amb grn
|
||
red | blblooD* C*A*Ta* iissww | org amb
|
||
fawn | blbloodd C*A*Ta* iissww | org amb
|
||
true red | **OOD* C***Ta* iissww | cpr org amb
|
||
cream | **OOdd C***Ta* iissww | cpr org amb
|
||
-----------------------+-------------------------+----------------
|
||
silver | B*ooD* C*A*Ta* I*ssww | grn
|
||
silver blue | B*oodd C*A*Ta* I*ssww | grn
|
||
silver chestnut | b*ooD* C*A*Ta* I*ssww | grn
|
||
silver lilac | b*oodd C*A*Ta* I*ssww | grn
|
||
silver red | blblooD* C*A*Ta* I*ssww | yel
|
||
silver fawn | blbloodd C*A*Ta* I*ssww | yel
|
||
true silver red | **OOD* C***Ta* I*ssww | org yel
|
||
silver cream | **OOdd C***Ta* I*ssww | org yel
|
||
|
||
The Oriental Solid Colors
|
||
|
||
The oriental solids are identical in every way to the standard solids
|
||
except in their names. Oriental color names tend to be used with cats
|
||
of oriental build, effectively solid-color Siamese.
|
||
|
||
Color | Karyotype | Usual eye color
|
||
----------------------+--------------------------+----------------
|
||
ebony | B*ooD* C*aa** iissww | grn
|
||
blue | B*oodd C*aa** iissww | grn
|
||
chocolate | b*ooD* C*aa** iissww | grn
|
||
lilac | b*oodd C*aa** iissww | grn
|
||
caramel | blblooD* C*aa** iissww | grn
|
||
fawn | blbloodd C*aa** iissww | grn
|
||
red | **OOD* C***T* iissww | grn
|
||
cream | **OOdd C***T* iissww | grn
|
||
|
||
|
||
|
||
|
||
|
||
----------------------------------------------------------------------
|
||
Feline Genetics Page 25
|
||
|
||
|
||
|
||
|
||
The Burmese Colors
|
||
|
||
The Burmese colors are formed from the standard solid colors by the
|
||
reduction in color expression from full, "C*", to the Burmese alleles,
|
||
"cbcb". This is a partial albinism and causes a slight reduction in
|
||
color intensity: black becomes sable. These colors are used almost
|
||
exclusively for the Burmese and related breeds, such as the Malayan
|
||
and Tiffany.
|
||
|
||
Color | Karyotype | Usual eye color
|
||
----------------------+--------------------------+----------------
|
||
sable | B*ooD* cbcbaa** iissww | gld
|
||
blue | B*oodd cbcbaa** iissww | gld
|
||
champagne | b*ooD* cbcbaa** iissww | gld
|
||
platinum | b*oodd cbcbaa** iissww | gld
|
||
cinnamon | blblooD* cbcbaa** iissww | gld
|
||
fawn | blbloodd cbcbaa** iissww | gld
|
||
red | **OOD* cbcb**T* iissww | gld
|
||
cream | **OOdd cbcb**T* iissww | gld
|
||
|
||
The Tonkinese Colors
|
||
|
||
The Tonkinese colors are formed from the standard solid colors by the
|
||
reduction of color expression from full, "C*", to combined Burmese and
|
||
Siamese, "cbcs". This is a partial albinism and causes a downgrade in
|
||
color expression, the body color becoming a light-to-medium brown and
|
||
the points becoming Burmese. These colors are used only with the
|
||
Tonkinese breed.
|
||
|
||
Color | Karyotype | Usual eye color
|
||
----------------------+--------------------------+----------------
|
||
natural mink | B*ooD* cbcsaa** iissww | trq
|
||
blue mink | B*oodd cbcsaa** iissww | trq
|
||
honey mink | b*ooD* cbcsaa** iissww | trq
|
||
champagne mink | b*oodd cbcsaa** iissww | trq
|
||
cinnamon mink | blblooD* cbcsaa** iissww | trq
|
||
fawn mink | blbloodd cbcsaa** iissww | trq
|
||
red mink | **OOD* cbcs**T* iissww | trq
|
||
cream mink | **OOdd cbcs**T* iissww | trq
|
||
|
||
The Siamese Colors
|
||
|
||
The Siamese solid-point formed from the standard colors by the reduc-
|
||
tion of color expression from full, "C*", to Siamese, "cscs". This is
|
||
a partial albinism and causes a downgrade in color expression, the
|
||
body color becoming fawn and the points becoming Burmese. The solid-
|
||
point colors are formed from the standard solids, the tortie-point
|
||
from the standard torties, the lynx-point from the standard tabbies,
|
||
and the torbie-point from the standard torbies. Only six of the eight
|
||
possible solid- or lynx-point and four of the six possible tortie- or
|
||
torbie-point colors are recognized.
|
||
|
||
|
||
|
||
|
||
|
||
----------------------------------------------------------------------
|
||
Feline Genetics Page 26
|
||
|
||
|
||
|
||
|
||
Color | Karyotype | Usual eye color
|
||
-----------------------+-------------------------+----------------
|
||
seal point | B*ooD* cscsaa** iissww | sbl
|
||
blue point | B*oodd cscsaa** iissww | sbl
|
||
chocolate point | b*ooD* cscsaa** iissww | sbl
|
||
lilac point | b*oodd cscsaa** iissww | sbl
|
||
red point | **OOD* cscsT* iissww | sbl
|
||
cream point | **OOdd cscsT* iissww | sbl
|
||
-----------------------+-------------------------+----------------
|
||
seal tortie point | B*OoD* cscsaaT* iissww | sbl
|
||
blue tortie point | B*Oodd cscsaaT* iissww | sbl
|
||
chocolate tortie point | b*OoD* cscsaaT* iissww | sbl
|
||
lilac tortie point | b*Oodd cscsaaT* iissww | sbl
|
||
-----------------------+-------------------------+----------------
|
||
seal lynx point | B*ooD* cscsA*T* iissww | sbl
|
||
blue lynx point | B*oodd cscsA*T* iissww | sbl
|
||
chocolate lynx point | b*ooD* cscsA*T* iissww | sbl
|
||
lilac lynx point | b*oodd cscsA*T* iissww | sbl
|
||
red lynx point | **OOD* cscs**T* iissww | sbl
|
||
cream lynx point | **OOdd cscs**T* iissww | sbl
|
||
-----------------------+-------------------------+----------------
|
||
seal torbie point | B*OoD* cscsA*T* iissww | sbl
|
||
blue torbie point | B*Oodd cscsA*T* iissww | sbl
|
||
chocolate torbie point | b*OoD* cscsA*T* iissww | sbl
|
||
lilac torbie point | b*Oodd cscsA*T* iissww | sbl
|
||
|
||
The Van Colors
|
||
|
||
The van colors are formed from the standard solid colors by the addi-
|
||
tion of the van gene, "Wv". This is a masking gene, covering the
|
||
effects of the agouti, color-expression, tabby, inhibitor, and white-
|
||
spotting genes. The van gene, a modified dominant-white gene, causes
|
||
the coat to be white with color on the crown of the head, ears, and
|
||
tail only. The preferred van color is auburn (orange). The tail is
|
||
often tabby-ringed.
|
||
|
||
Color | Karyotype | Usual eye color
|
||
----------------------+--------------------------+----------------
|
||
black van | B*ooD* ****** ****Wv* | org wbl odd
|
||
blue van | B*oodd ****** ****Wv* | org wbl odd
|
||
chestnut van | b*ooD* ****** ****Wv* | org wbl odd
|
||
lavender van | b*oodd ****** ****Wv* | org wbl odd
|
||
cinnamon van | blblooD* ****** ****Wv* | org wbl odd
|
||
fawn van | blbloodd ****** ****Wv* | org wbl odd
|
||
auburn van | **OOD* ****** ****Wv* | org wbl odd
|
||
cream van | **OOdd ****** ****Wv* | org wbl odd
|
||
|
||
The Whites
|
||
|
||
White is not a color, but rather a masking of the color genes result-
|
||
ing in an absence of color. There are five ways a cat can have an all
|
||
white coat: be full-inhibited white, be full-spotted white, be domi-
|
||
nant white, be blue-eyed albino, or be albino. Each of these ways is
|
||
genetically different.
|
||
|
||
|
||
----------------------------------------------------------------------
|
||
Feline Genetics Page 27
|
||
|
||
|
||
|
||
|
||
|
||
The full-inhibited white coat comes from a 100% expression of the
|
||
inhibitor gene, "I*", masking all colors and patterns. Since the
|
||
current trend in chinchilla coats is to have just a hint of tipping,
|
||
certain kittens are bound to be born where the "hint" is effectively
|
||
zero, creating an all-white cat. Since the colors still exist, the
|
||
eyes will be the proper color for the masked "true" coat colors, and
|
||
may be anything except dominant-white blue, albino blue, or pink.
|
||
|
||
The full-spotted white coat comes from a 100% expression of the white
|
||
spotting gene, "S*", masking all colors and patterns. This coat may
|
||
have a few non-white hairs, especially on a kitten. Like the full-
|
||
inhibited white, the eyes will be the proper color for the masked
|
||
"true" coat colors, and may be anything except dominant-white blue,
|
||
albino blue, or pink.
|
||
|
||
The dominant white coat comes from expression of the dominant-white
|
||
gene, "W*", masking all colors and patterns. The eyes are always
|
||
orange, dominant-white blue, or odd.
|
||
|
||
The blue-eyed albino comes from expression of the blue-eyed albino
|
||
allele of the albino gene, "ca*", masking all colors and patterns.
|
||
The eyes are always albino blue.
|
||
|
||
The albino coat comes from expression of the albino allele of the
|
||
albino gene, "cc", masking all colors and patterns. The eyes are
|
||
always pink.
|
||
|
||
Color | Karyotype | Usual eye color
|
||
----------------------+--------------------------+----------------
|
||
full-inhibited white | ****** ****** I***** | not wbl/abl/pnk
|
||
full-spotted white | ****** ****** **S*** | not wbl/abl/pnk
|
||
dominant white | ****** ****** ****W* | org wbl odd
|
||
blue-eyed albino | ****** ca***** ****** | alb
|
||
albino | ****** cc**** ****** | pnk
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
----------------------------------------------------------------------
|
||
Feline Genetics Page 28
|
||
|
||
|
||
|