Color genes

[offherrocker]

I realize I have crap for rex rabbits...but I noticed my castor doe seems to throw a LOT of castors....even though she was bred to a tri broken. How would that work? Previous litter had several castor as well.

 

[Alaska Satin]

I realize I have crap for rex rabbits...but I noticed my castor doe seems to throw a LOT of castors....even though she was bred to a tri broken. How would that work? Previous litter had several castor as well.

Castor is produced by all dominant genes except at the broken <en> locus: <A_B_C_D_E_enen> So at least some of her kits will likely inherit her dominant genes, thus looking like castors. Even if the buck was entirely recessive <aabbccddee> (that's a lilac tort under cover of REW) you would probably get some or even many castors.

If your doe is homozygous for all of the genes, i.e. <AABBCCDDEEenen> you'll almost certainly get castors no matter what you breed her with. If she carries recessives at any of her "second-place" blanks you'll still probably get castors, but also other colors as well, depending on the buck.

If you breed her with a tricolor, which is a broken harlequin <A_B_C_D_ej_Enen> and you get only castors and broken castors, it suggests that at the very least she's homozygous at the <E> locus, i.e. she is <A_B_D_D_EEenen>.

You may be able to figure out what she carries in her other second places by noting the colors of her kits when bred to a particular buck. Was her previous litter by the same buck, and what colors were in that litter?

 

[judymac]

Castor is produced by all dominant genes except at the broken <en> locus: <A_B_C_D_E_enen>

Well said. Since castor is the most dominant color, you always expect a LOT of castors in the litter. This is normal. For each gene, the rabbit gets one copy from each parent, two in total. A rabbit must have both recessive genes for a recessive gene to be expressed, to look that color. If a rabbit has both a dominant and a recessive gene, like inheriting black from your doe and maybe chocolate or lilac from the dad, the rabbit will look like whatever the dominant genes are, in this case the bunny will have black-based colors. If, however, you mate this rabbit with both black and chocolate genes to a chocolate, you have a 50/50 chance that a kit born to that pairing will get both recessive chocolate genes, and be chocolate-based. That's how you end up with other colors in the litter, even when mated to a dominant color parent

.The ABCDE alphabet soup means that your doe is:

A-agouti. This is wild rabbit pattern, with white inside the ears, around the eyes, on the belly; and multiple bands of colors on a single hair--in this case gray at the base, yellowish in the middle, and chestnut on the outside with black tips. (Cinnamon aka chocolate agouti, lynx, opal and orange are all also agouti color patterns, with different recessive genes in play. Cinnamons have brown instead of black, lynx have brown and dilute, opal has dilute with the black, and orange is non-extension.) Agouti is dominant to self colors like all black or all chocolate.

B--black. There are two choices here, dominant black-based colors (like black or blue, castor or opal), or recessive brown-based colors (like chocolate or lilac, cinnamon or lynx). Your doe has dominant black here, which is why the agouti base color on the hair is slate gray and the tips are black.

C--color. This gene has five choices on it. Full color (which includes your castor color) is the most dominant. Under this comes chinchilla, sable, Himalayan (aka pointed white or Californian pattern), and albino red (or ruby)-eyed-white. Breeding your castor to any of these patterns will likely result in mostly dominant full color kits, unless the doe carries recessives for any of these.

D--dense/dilute. This gene determines whether all of the color gets delivered to the hairshaft (dense color), or just some of it (dilute color). Blue is the dilute of black, lilac the dilute of chocolate, and cream/fawn (depending on breed) the dilute of orange. Your castor is a dominant dense color.

E--extension. It's a funny name for this gene, but this determines how the dark color gets extended along the agouti hairshaft, which is why it's called 'extension'. There are five options on this gene as well. This gene is unique in that the normal dominant 'wild rabbit' color, called Normal Extension, isn't the MOST dominant color. It is dominant over harlequin (tricolor is just harlequin plus the broken gene), which puts the agouti bands of color on different patches of skin instead of different rings on one fiber. The most recessive choice here is called non-extension, where no dark color goes down the main body hair--this is where your oranges, reds, and tortoiseshells come in. There are two things more dominant than Normal Extension, that would be a very rare gene called Dominant Black, where dark color completely covers all the agouti bands, making the rabbit look like a self black. The next most dominant one, more dominant than normal extension, is steel, where the dark undercolor gets pushed up the hairshaft, leaving the yellowish middle band out on the fiber tips. That's why it's called gold-tipped steel. (If you have a steel chinchilla, the middle band is pearly white, so they end up being silver-tipped steels, but that's another story.)

 

[offherrocker]

Castor is produced by all dominant genes except at the broken <en> locus: <A_B_C_D_E_enen> So at least some of her kits will likely inherit her dominant genes, thus looking like castors. Even if the buck was entirely recessive <aabbccddee> (that's a lilac tort under cover of REW) you would probably get some or even many castors.

If your doe is homozygous for all of the genes, i.e. <AABBCCDDEEenen> you'll almost certainly get castors no matter what you breed her with. If she carries recessives at any of her "second-place" blanks you'll still probably get castors, but also other colors as well, depending on the buck.

If you breed her with a tricolor, which is a broken harlequin <A_B_C_D_ej_Enen> and you get only castors and broken castors, it suggests that at the very least she's homozygous at the <E> locus, i.e. she is <A_B_D_D_EEenen>.

You may be able to figure out what she carries in her other second places by noting the colors of her kits when bred to a particular buck. Was her previous litter by the same buck, and what colors were in that litter?

Pretty much the same as this litter and same buck. I did keep a castor out of that litter, but was really unsure when I tried to sex it. I THINK its female....I hope lol.

 

[offherrocker]

Would I be better off trying to stick with castors then? Since it sounds like they are an easier color? She also threw several Charlie's in the past with that buck and a solid Harlequin...which I kept even though I know he's not an accepted color. I really needs to change out my breeding back since he's kind of small...and I hear that tris are kind of a pain, lol.

At some point I hope to get my hands on some good otters...but that may not be until next year.

 

[Alaska Satin]

Pretty much the same as this litter and same buck. I did keep a castor out of that litter, but was really unsure when I tried to sex it. I THINK its female....I hope lol.

It sounds like one or both of your rabbits carries very few recessives, then (other than the harlie <ej>).

Would I be better off trying to stick with castors then? Since it sounds like they are an easier color? She also threw several Charlie's in the past with that buck and a solid Harlequin...which I kept even though I know he's not an accepted color. I really needs to change out my breeding back since he's kind of small...and I hear that tris are kind of a pain, lol.

It depends on what you mean by an easier color. If you mean easier to get it to show up in your litters, that can include either castor, selfs, REW or BEW. As long as you keep castors, you'll probably keep getting castors, though lots of other varieties can hide behind the dominant genes. The latter three varieties, self, REW and BEW, are "easy" since when you breed one to the same - self x self, REW x REW or BEW x BEW - you'll only get self, REW or BEW, respectively. But beware, a lot of genetics can hide behind those colors as well, and as soon as you breed your castor, self, REW or BEW to a rabbit with other genetics, you might get a lot of surprise colors and patterns.

However, if you're trying to breed to the standard, in other words get show-quality varieties, castor is neither the easiest nor the hardest. There are numerous factors to consider in castors including surface color, ring color, and ring width and definition. They do tend to have good texture and density but that can vary with the animal and line.

I'm not sure I'd say that tricolor is a pain... it can be a pain to get, but you've got it. It helps to think of it as simply a broken harlequin. I wouldn't necessarily be quick to get rid of it, as tricolor rabbits can be very flashy and popular for people looking for a unique and beautiful pet. Proper harlequins and tricolors are agouti-based, so breeding castors with tricolors is not a bad thing.

The caveat is that the harlequin allele can hide partially but not totally, and mess up other colors, including castor. So you should look closely at your castors, especially the ones you keep, and especially if you decide you want to eliminate the harlies/tris. You will probably find "harlequinized castors" which have faint harlequin markings within the normal castor color, making the rabbit an unshowable variety (but still possibly useful for breeding). The markings often show up on the face and ears, but can really be anywhere on the rabbit. Here are some examples from a great page to look at to understand rex colors - Mini Rex Color Guide: