Cat Coat Color and Genetics

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The genetics of cat coat characteristics is a complex subject, and many different genes are involved.

The genes involved with coat color include:

• the White masking gene, W. It is dominant and masks all other colors. A cat that is WW or Ww will be white, no matter what other color genes it has. A cat that is homozygous recessive (ww) will express the fur colors of the Orange gene.
• The Orange gene, O, determines if there will be orange fur (often referred to as ginger, red, gold or yellow). In its dominant form, O, the fur will be orange. In its recessive form, o, the fur will be a shade of black, based on the B gene.
• The B gene. In its dominant form, B, will produce a black color; other, recessive variants are b, producing brown (or chocolate), and b¹ producing light brown or cinnamon.
• the Dense pigment gene, D, corresponding to the dilute gene, d. When a cat has two of the recessive d genes, black fur becomes 'blue' (ie grey), brown hair becomes lilac, and orange fur becomes cream (or a shade of beige). This is known as maltesing, and a grey or 'blue' cat is sometimes referred to as a maltese.  Blue-cream cats are normally female only, for reasons similar to the calico or tortoiseshell colorations.
  

The genes involved with coat pattern include:

• the white Spotting gene, S, which has variable expression, so that an SS cat has more white patches than an Ss cat. It is this gene that creates cats with the familiar white blaze across the face, a white bib, or dappled paws.  There is typically more white at the bottom of the coat (nose, chest, paws).  

  White spotting can occur in combination with any of the colors and patterns already described. The customary way of describing the pattern is to add "and White" to the name of the color and pattern of the cat. 

  A black cat with the white spotting gene, giving it a white 'shirtfront' and 'socks' is often referred to as a tuxedo cat, or sometimes a jellicle cat .   

  There are different names for the different amounts of white caused by the spotting gene:

  • A "mitted" cat just has white paws.
  • A cat with a white spot on its chest has a "locket."
  • A cat with one or more little white belly spots has "buttons."
  • A "bi-color" is about half white.
  • A "harlequin" is mostly white with several large patches of color.
  • A "van" is almost all white with color patches only on the head and tail.
    
• the Inhibited pigment gene, I, that produces tipped hairs that are pale but colored at the tip.  'Smoke' cats are similar to a solid colored cat, except that the roots of the hair are white.
  
• the agouti gene, A. The dominant A causes banded, ticked or agouti  hair (appearing lighter) between tabby markings of solid colored hair, while the recessive non-agouti, a, causes non-banded hair of an identical color to the tabby stripes, and therefore a uniform coat color - a solid colored or 'self colored' cat. The non-agouti gene does not effect the dominant Orange gene, which always shows a tabby pattern.
  
• the tabby gene, T/Ta/tb, which sets the basic pattern of stripes that underlies the coat: 
  • the basic wild-type tabby gene, T, produces what is called a mackerel, striped or tiger tabby; this may be modified by other genes to produce a spotted tabby pattern
  • a dominant mutant, Ta, produces a ticked or Abyssinian tabby, with agouti or ticked fur, and no tabby markings, except on its face. 
  • while a recessive mutant, tb, produces a blotched or classic tabby pattern.

For a cat to be tortoiseshell (random mottled patches of black & orange or blue & cream) or tortie, it must simultaneously express two alleles, O and o, which are located on the X chromosome. Males normally cannot do this, as they have only one X chromosome, and therefore only one allele, and so tortoiseshell cats are normally only female.  

A patched tabby is similar to a tortoiseshell, but the patches tend to be larger, and show a tabby pattern.  It is sometimes referred to as a torbie

A calico cat is a tortoiseshell or patched tabby cat with the white spotting gene, showing a large amount of  (mostly) white, with spots of black & orange or blue & cream, depending on whether the cat has the dense or dilute gene.

It could be deduced that a grey male cat with a white bib and paws:

• has the o variant of the orange gene on its only X chromosome (because the grey color corresponds to black, not orange)
• has at least one S variant of the white Spotting gene (because it has the white bib and paws)
• has two w genes (because it expresses a fur color other than white)
• has the dominant B gene (because its fur color is a shade of black rather than brown)
• has two d (dilute) genes (because its fur is grey, rather than black)

Genes for other coat characteristics include:

• The Long hair gene which governs cat fur length. The dominant form, L codes for short hair, and the recessive l codes for long hair.
  
• Different genes for curly coats which produce the curly coats of the Cornish Rex, Devonshire Rex, LaPerm and Selkirk Rex breeds.
  
• A gene for hairlessness, which produces the Sphynx cat.

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Cat Coat Genetics" and from Cat-Purr.com

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