Color and Genetics
I get a lot of people who ask me about colors of our kittens- especially the black kittens! "How do you get so many black kittens if you have no black cats??" The reason is simple enough- because we have a lot of blue cats!
Okay, maybe that doesn't sound so simple. Color genetics can become very complicated, but I'll try to provide here a very simplistic overview so that you can better understand how we produce kittens of such a variety of colors.
Basic
Overview on Color Gene
B and D
Genes
Genes for Basic Colors
Color is produced by special pigment chemicals called melanin. Pigment is produced in special cells called melanocytes, which are found within the hair, skin, and eyes- we're only looking at hair/fur in this overview.
The two basic pigments that contribute to coloration are black and yellow pigments. It is the interplay between the expression of genes for these two basic pigments that give the cat its basic coloration. It is important to realize that a single hair can be all black, all yellow, or have bands of black and yellow pigment.
All of the colors we work with in my cattery are found in the Locus B, D, and O gene pool. Each Locus is responsible for different coloration.
The color modifying genes do not make the color pigments, but they do influence the shade of the color, usually by reducing its intensity (washing it out). Two of the primary modifying genes include Brown (Locus B) and Dilution (Locus D)
Brown (Locus B)
The Brown gene (Locus B) in the cat affects the intensity of black pigment. Brown is a recessive trait that will modify the normal black pigment (B) to a brown (chocolate) color (b/b) or to a cinnamon color (b’/b’). Normal coloration is dominant over brown, which in turn is dominant over cinnamon.
Dilution (Locus D)
Dilution is another gene that modifies the normal colors and will wash out or dilute both black pigment and yellow pigment. Dilution is a recessive trait that will modify normal black pigmentation to give a grey color (d/d) often called Blue. Dilution can combine with B locus Brown (b/b) to give Lilac (Lavender) coat color and with B locus Cinnamon (b’b’) to give Sable (Fawn) coat color.
The color modifying genes do not make the color pigments, but they do influence the shade of the color, usually by reducing its intensity (washing it out). Two of the primary modifying genes include Brown (Locus B) and Dilution (Locus D)
Brown (Locus B)
The Brown gene (Locus B) in the cat affects the intensity of black pigment. Brown is a recessive trait that will modify the normal black pigment (B) to a brown (chocolate) color (b/b) or to a cinnamon color (b’/b’). Normal coloration is dominant over brown, which in turn is dominant over cinnamon.
Dilution (Locus D)
Dilution is another gene that modifies the normal colors and will wash out or dilute both black pigment and yellow pigment. Dilution is a recessive trait that will modify normal black pigmentation to give a grey color (d/d) often called Blue. Dilution can combine with B locus Brown (b/b) to give Lilac (Lavender) coat color and with B locus Cinnamon (b’b’) to give Sable (Fawn) coat color.
As you can see in the image above, when the D Locus is paired with the B Locus, nearly all of the time it will result in another B Locus color. It is possible to get the recessive D, but far less likely.
O Genes
Orange (Locus O)
The Orange gene (Locus O) gives the Red/Orange coloration of cats and is interesting for two reasons. First of all, it is unique to cats. Secondly, it is found on the X chromosome, making the Orange coloration sex linked. There are two versions of the gene, the dominant Orange (O) allele and the recessive, wild-type non-orange (o) allele.
Orange (O) generally blocks black pigment formation and forces only yellow pigment (pheomelanin) to be formed. Non-orange (o) allows both yellow and black pigment to be formed. Female cats, possessing two X chromosomes, can have orange coloration (O/O), orange and black coloration (o/o), or a mottled mix of orange and black coloration called Tortoiseshell (O/o).
Male cats, with only one X chromosome cannot normally be tortoiseshell; the rare males that are usually have an extra X chromosome (XXY).
The Dilution gene can also influence Orange pigmentation (Locus O), which it washes out to give a Cream coloration.
Wonderful
White
Genes for White Spotting
White markings are a prominent feature of cat color genetics. Interestingly, white is not a color, but is rather a lack of color. In fact, white results from a developmental lack of cells (called melanocytes) that produce pigmentation.
Dominant White (Locus W)
Dominant White, from Locus W, can give an all-white cat. Dominant White as it’s name indicates is dominant in that only one copy of the mutated gene (W) is needed to give the trait. The recessive and normal version of the gene is called w. Dominant White will mask the effects of the and Brown and Cinnamon (Locus B) genes. Dominant white can be confused with recessive white (albino, c/c, coming from the C locus).
White Spots (Locus S)
Cats can have a full range of white markings, from none, to moderate, to predominant. The Locus S is involved in producing white markings, but the gene has not been cloned and it is not known if Locus S represents one gene or several genes.
Cats are graded based on the degree of white they contain, with a completely white cat being a 10 (high grade white). Even these high grade whites will generally be born with at least one spot of grey on their heads.
