Steel rabbit genetics. How do you know your rabbit carries an Es (steel) gene when the sneaky gene is hiding? We’ll help you figure out the steel rabbit genetics.
The 'steel' gene is a part of the E locus. Need a refresher in E locus rabbit colors? This link will open a new window, so you can return here easily.
The 'Es' gene results in the undercolor extending all the way up the hair shaft, wiping out the ring, and eliminating the white belly on an agouti. Steels can come in black, blue, chocolate or lilac, and either gold-tipped or silver-tipped.
Agoutis that express their yellow pigment (castors, chestnut
agoutis, etc.) turn into gold-tipped steels in the presence of a single Es gene.
Agoutis with yellow pigment suppressed (chinchillas) will become silver-tipped steels. Tan-patterned rabbits can also be steeled, as can selfs.
Double the ‘Es’ gene (EsEs), and, depending on the strength of the modifiers, you may get a rabbit that is virtually black--so dark as to overpower even the tipping. But, we suspect you might be able to find a clue somewhere in its fur...some snippets of color...that indicate the rabbit may not be a simple black rabbit.
Because of its nature, the 'Es' gene occasionally seems to play tricks.
As a dominant gene, an Es supposedly cannot hide. A rabbit cannot be a steel if neither of its parents are steels. BUT: What if you have no idea that your “black” rabbit is actually an agouti black (double-steel)?
Depending on how the Es gene is
paired with other E-locus alleles, its more easily recognized effects might be obscured.
Depending on how the Es gene is paired with other E-locus alleles, its effects might be obscured.
According to A.G. Searle, Comparative Genetics of Coat Colour in Mammals, and Roy Robinson, Colour Inheritance in Small Livestock:
In other words, this agouti rabbit will appear completely black with minimal to no ticking to give away the presence of the steel gene. The ‘e’ allele apparently has the capability of toning down the ticking effect of the steel gene, which hints at some degree of incomplete dominance.
Additionally, in a self rabbit – aaEse – the ticking may not be present at all, and the steel gene therefore doesn’t show at all. It’s black on black, with no ticking, thanks to the “e” allele. (But a self black carrying aaEsE will demonstrate the usual steel ticking on a black rabbit.)
The following combinations at the E-locus will result in a possibly hidden Es gene. There may or may not be any ticking that would give its presence away, depending on modifying factors:
A_EsEs – Agouti double steel
A_Ese – Agouti with 1 steel and 1 non-extension gene
aaEsEs – Self color double steel
aaEse – Self color with 1 steel and 1 non-extension gene
(Tan pattern rabbits may have a greater propensity to not lose the minor ticking completely, therefore less likely that the Es gene would hide in a tan-pattern gene pool, according to Huffmon.)
Use the pedigree and test-breeding with EE or ee animals to identify which of those apparently ‘self’ rabbits actually carry one or more steel genes.