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Cats/Siamese genetics

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Expert: - 1/1/2011


Question

my cat
Hello!

I would like to ask a seriously "scientific" question :)
I'm a proud owner of a gorgeous traditional Siamese male, and I'm at university learning biotechnology, meaning I'm super interested in genetics. What I would like to know is:
My boy is the son of two seal point Siamese, but his colour differs pretty much from his parents'. And by different I don't mean blue, I mean he's rather chocolate.
No matter how much I searched, I just couldn't find out if seal or chocolate point is the recessive phenotype. What I know is, Siamese colour depends on four genes, and the second one (bb or BB) decides if he's seal, or chocolate.

Please help me out with a little information, I'm eagerly looking for an answer for half year :)

Thank you in advance, and happy new year!
Livia

Answer
Livia,

Happy new year back at ya'!!!!!!!!!

The best source of feline coat color genetics is the latest edition of Roy Robinson's "Genetics for Cat Breeders".

I do know one of the authors and have much faith in the accuracy of this text, based on what we know currently.

To get back to your question:  The so-called brown gene has three alleles. The B is the wild gene and will give you seal point, if no other modifier is in place (e.g. the density gene [Dd]. or the sex linked orange gene [Oo], etc.).

To get chocolate, both parents must be carrying the b (chocolate) allele and the progeny may be homozygous for bb.  So, BB, Bb, bB will give you seal, and bb will give you chocolate.  There is one other allele of the brown gene, called cinnamon allele, denoted b1.  Cinnamon is recessive to chocolate which is recessive to the wild allele. Cinnamon rarely occurs in Siamese, so I would not worry about it, but here is the full breakdown:

BB, Bb, bB, Bb1, b1B all give you seal.  bb, bb1, b1b would give you chocolate, and b1b1 would give you cinnamon.  The archetypal cinnamon cat is the so called red or sorrel Abyssinian.

I hope this helps.

Seasonal regards... Norm.  
    Questioner's Rating
    Rating(1-10)Knowledgeability = 10Clarity of Response = 10Politeness = 10
    CommentThank you very much :) You have helped a lot! All the best, Livia


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Norman Auspitz

Expertise

I can answer most non-veterinary questions about cats. My particular expertise is pedigree cats, breeding and showing. However, I am versed in feline behavior, cat breeds and their characteristics, general feline husbandry, and the like.

Experience

I judged for the Canadian Cat Association from 1975 until 1982. I am currently an approved allbreed judge for the Cat Fanciers'' Association (the world''s largets cat registry), and have been judging for them since 1991. I have been breeding pedigreed cats since 1971 and have been exhibiting pedigreed cats in shows since 1970. I obtained my first pedigreed cat in 1970 and have never looked back. In 1971, I obtained my first Abyssinian which has become my primary breed. In addition, I have bred Manx and Persians. Currently, besides the Abyssinians, I am also breeding Maine Coons.


Organizations
Cat Fanciers'' Association, inc. (CFA) and the Manx, Maine Coon, and Abyssinian breed councils. I am currently Abyssinian breed council secretary.

Publications
Cat Fancy Magazine, The Abyssinian Chapter in The Cat Fanciers'' Association Complete Cat Book, and Articles for various editions of The Cat Fanciers'' Association Yearbook

Education/Credentials
I received a B.S. from Drexel University in 1968, a M.Math from University of Waterloo, in 1970, a Ph.D. from University of Waterloo in 1975, and a MBA from McMaster University in 1980. I received my approved allbreed judging status in the Cat Fanciers'' Association in 1999.

Awards and Honors
We have produced a number of Cat Fanciers'' Association (CFA) National winning Abyssinian and Maine Coons. We have produced a number of Abyssinian and Maine Coon Distinguished Merit females (an award for a top producing cat), including the first Distinguished Merit Abyssinian in the red (sorrel) color. I am the CFA Abyssinian breed council secretary and belong and/or hold office in a number of cat clubs. I am also a member of the CFA Judges Association.

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