Hey! I was wondering if anyone knows/has examples of what steel & the colorpoint genes (aside albino, of course, such as sable & chinchilla,) effects reds/torts? I know chinchilla + harlequin makes magpie, so I assume the effect would be similar in a chinchilla red appearing just mostly white with maybe some eumelanin showing through if the red was smutty, and tort would just replace the red points with white as well?
I also am curious about how steel effects red/tort/harlequin as well! If anyone knows
A
red is a
non-extension chestnut agouti <
A_B_C_D_ee>. Non-extension <
ee> interferes with the extension of the black bands of an agouti. I find it helpful to imagine a wild type rabbit as having orange hair, with black pigment laid over the orange in alternating bands, to produce the characteristic agouti ring color. Non-extension <
ee> prevents the black from moving up the hair from the base (so the undercolor becomes white or cream instead of slate, among other effects). Sometimes the <
ee> allows a little bit of the terminal band to show, which in an orange or red is called "smut." This seems to depend in part on modifiers that affect the non-extension action, as well as some other alleles like wideband <
w>.
A
tort is a
non-extension self black <
aaB_C_D_ee>. Imagine the self black rabbit as an orange rabbit with the black pigment, which usually overlays the orange in bands on the wild type agouti, increased to cover the hair entirely. Then you can imagine that the non-extension <
ee> blocking that black pigment, leaves the orange rabbit underneath the black exposed. Again, modifiers and other genes affect how much "smut," which in this case makes up the characteristic markings of a tort, will remain. Good torts have clear orange over the top, with the black tending to appear on the extremities and other areas of shorter fur; but some torts have extremely heavy smut/tipping, like this Mini Rex doe who is showing a molt pattern, but is also very dark:
The chinchilla allele <
c(chd)> (as well as all alleles farther down the dominance hierarchy, which are sable <
c(chl)>, himalayan <
c(h)> and REW <
c>) prevents expression of most or all yellow pigment, so there will probably never be such a thing as a red chinchilla rabbit (or a red sable or a red himalayan). In a harlequin, a <
c(chd)> in the dominant C position means the harlequin loses its orange but keeps its black, which is called magpie. This is true as well of a sable <
c(chl)> harlequin, which also looks like magpie but with muddier dark areas (sepia instead of black, since the <
c(chl)> allele messes with the black pigment as well as completely blocking the yellow pigment).
If a rabbit is a non-extension
agouti (red) but also has a chinchilla <
c(chd)> or sable <
c(chl)> in the dominant position at the C locus, it's called an ermine or frosty. The homozygous non-extension <
ee> prevents the normal extension of black pigment in the fur, while the chinchilla and sable alleles prevent expression of most or all yellow pigment in the fur. That leaves a dark-eyed but otherwise almost colorless rabbit, though a haze or "veil" of black tipping is often, though not always, left on the shorter hairs (similar to the tort pattern leaving the dark tipping on an orange rabbit) or even all over. The Czech Frosty is a non-extension chinchilla, selected for relatively heavy tipping:
Image from the Czech Frosty Rabbit Club page https://czechfrosty.com/287-2/
If instead the rabbit is a non-extension
self but also has a chinchilla <
c(chd)> or sable <
c(chl)> in the dominant position at the C locus, it's basically a tort without the orange, called a sallander <
aaB_c(chd)_D_ee>
or a sable point <
aaB_c(chl)_D_ee> (this doe is also very dark).
Steel <
E(S)> requires a dominant agouti <
A> to express properly. The steel allele causes the dark bands of the agouti to be squished up to the top of the hairshaft, like this:
But since reds and torts are <
ee>, there is no room for a steel <
E(S)> allele.
Steel <
E(S)> impact on harlequin <
e(J)> is an interesting question. They're both at the same locus so the rabbit would be <
E(S)e(j)> . While steel is at the top of the dominance hierarchy, <
e(j)> is known for its partial dominance. In this case, it would probably depend on what the rabbit had at its A locus. Self <
aa> neutralizes both the <
E(S)> and the <
e(j)>, so the rabbit would just be black. If the rabbit was agouti <
A_>, my suspicion is that because in harlequin black and orange are distributed onto different hairs, rather than onto different parts of each hair, steel would have little effect; i.e. there are no bands to mess around with.
However, according to the wonderful
Phenotypes of A-/E- Gene Combinations chart on Green Barn Farm's website
https://www.gbfarm.org/rabbit/steel-phenotype-chart.shtml, an agouti <
E(S)e(j)> would be black with possible patches of ticking. (Incidentally, that chart suggests that an agouti rabbit heterozygous for steel and non-extension <
E(S)e> would also be black, possibly with some areas of ticking.)
