When I posted on Claudia's AG_Angoras_Community yahoo group that I am developing Otter (to eventually be Tan) angoras, I got a lot of interest and questions about red, wideband, and otter genetics. Now I am no expert on genetics, but I have bred animals almost all my life, from cavies to horses, and I study a lot, so I *think* I have a pretty good grasp of what these particular genes are about. I'm writing this assuming that the readers have a basic grasp of rabbit color genetics. So here goes:
Reds are essentially Chestnuts or Chocolate Agoutis with the non-extension gene ee and rufous modifiers to intensify the red. The recessive ee removes all or most of the black pigment in the hair shaft. For some reason in Agoutis it does a more complete job than in selfs, demonstrated by the relatively clean color of Reds and Fawns compared to the masks on Torts. Reds with Chocolate, or bb, instead of B_ for Black seem to have the cleanest color. I suspect the reason for this is, being lighter, Chocolate colored smut just blends in better. Reds without the wideband gene will have light colored bellies. The recessive wideband gene ww plus rufous modifiers is what colors in the bellies of Reds and Tans. The wideband gene works by doubling the size of the yellow intermediary band of the hair shaft.
So the ideal genetics of a self red would be AAbbCCDDeeww + rufous. However, some variation will work, so the combination of A_B_C_D_eeww + rufous works also.
Tans and Otters:
The Tan pattern is represented by at. It is recessive to A, or Agouti, but dominant over a, or Self. They come in all 4 self colors, Black, Blue, Chocolate, and Lilac. A rabbit with the Tan pattern looks kinda like a self-colored rabbit that scampered through some paint. It's belly, chest, parts of its legs, triangle, eye circles, nostrils, and pea spots in front of the ears, are light or red colored, depending upon other factors. The other factors are wideband, rufous, and chinchilla. It also will have brindling on its flanks and quarters where the belly color meets the self color.
A Tan rabbit's genetic code is ideally atat??CC??ww + rufous. Since at is recessive to A, a Tan can only have another at or an a in the second position.
What makes a Tan different from an Otter or a Marten?
An Otter does not require the wideband gene. As a result, the tan markings will be smaller, will not go clear down to the skin, and will have a slate undercolor. There will be little if any brindling.
A Marten has at least one chd, or chinchilla, gene ideally paired with another chd or a c. The chin gene removes the yellow from the hair shaft, leaving only black or a silvery color. The wideband gene is not necessary in a Marten, but I feel it does make them more striking, as it increases the size and depth of the silver markings.
Self Reds have been produced from rabbits with the atat genes. Reportedly, they are Tans with the ee gene. An Otter with the ee gene results in what we call a Fox or Tort Marten.
More information on these genes can be found in Rabbit Coat Color Genetics by Glenna M Huffman.
I hope this answers some questions, it took awhile for me to understand it as well as I do, and I still have many questions myself. But if you really want to know more, read Glenna's book. It is well worth the time spent!
And of course, the obligatory pics: :)