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cat coat genetics
The genetics of cat coat coloration, pattern, length, and texture is a complex subject, and many different genes are involved.
== Genes involved in albinism, dominant white, and white spotting ==
* The "C" gene codes for the enzyme tyrosinase, the first step in pigment production. Its recessive alleles determine whether a cat is a complete albino (pink-eyed) or a temperature sensitive albino. The temperature sensitive albino genotypes are cbcb Burmese (sepia), cscs Siamese (pointed), and cbcs Tonkinese (mink). The cscs gene can turn a cat's eyes blue due to a reduced number of melanocytes, affecting pigmentation of the eyes. If a cat has the dominant C allele, then the cat is non-albino and full pigment production occurs.
* The ''white masking'' gene, ''W/w''. The "W" gene prevents the normal replication and migration of pigment-producing cells during embryologic development. As a result, ''WW'' and ''Ww'' cats have a greatly reduced number of melanocytes and appear white, no matter what other color genes it may carry. Only a cat that is homozygous recessive (''ww'') will express normal pigmentation. Thus, ''W'' is epistatic to the other coat pigmentation genes. Some cats with the ''W'' allele of this gene are deaf and/or have depigmentation of the iris of one or both eyes, resulting in blue eye color. White cats are also more likely to get skin cancer.
* The ''white spotting'' or ''piebald spotting'' gene, ''S/s'', has variable expression, so that an ''SS'' cat often has more extensive white patching than an ''Ss'' cat. It is this gene that creates the familiar white blaze across the face, a white bib, ''tuxedo'' pattern, or dappled paws. A hypothetical Sb allele ("gloving gene") may cause the mittens in Birman and Snowshoe breeds. Some researchers believe that there are separate white spotting genes for distinct forms of white pattern, such as the white locket that some cats have on their neck or bellies.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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