Question about Ed (Dominant Black) on bb or dd rabbits

[user 7388]

So, my understanding of dominant black is that it overrides everything and extends black through the entire length of the hair, no matter the rest of the genotype.
However, my understanding of bb is that it weakens eumelanin so that black becomes brown, and my understanding of dd is that it causes a defect in eumelanin production leading to dilute blue/lilac.

If a rabbit has both Ed and one of bb/dd, and let's go so far to say it's bbC_ddEd_, then the rabbit's biochemistry is such that eumelanin is defective and weakened. Dominant black should extend eumelanin all the way down the hair shaft, but in this case, the eumelanin also shouldn't work right. What's the resulting phenotype?

Thanks in advance!

 

[Zass]

The recessives at the color locus are actually the one that can override any other. (cc Ruby eye white covers everything, including any extension gene. )
Other C locus genes would also effect the coat, even of an Ed_, the same way they still effect steel rabbits.



There isn't a lot known about Ed, and it's very hard to pin down whether or not it's actually present in a herd.
Since the visual appearance of a Ed_ is exactly the same as a recessive self aa, the appearance will the the same even diluted.

The genotype you have above should have the visual appearance of a self lilac, the same as aa bb C_dd .

Think of it as still extending that weakened eumelanin evenly down the entire hair shaft.

 

[user 7388]

Ah, that makes sense and kind of what I expected. So "dominant black" isn't a great name for Ed, as it more mimics homozygous self on the A locus. It would extend the black (or base colour) in a chin all the way down the hair shaft as well then, I presume, since chin just knocks out pheomelanin...

So what would cch1_Ed_ look like then? The C locus overpowers the E locus normally (at least it would for ccEd_) but there are steel sables, cch1_Es_, right? So would Ed turn sable into more of a self? What about ch_Ed_?

I love the way C and E interplay; one of my first rabbits was an ermine cch3_ee and is what got me interested in the genetics side of things!

 

[SableSteel]

Ed doesn't affect the stuff that happens on the b, c, d, etc. It just covers up the patterns on agouti and makes the rabbit look visually self (aa E_)
cchd Ed would appear self chin. Same as aa B_ cchd_ D_ E_. _ B_ cchl c or cchl ch D_ Ed would appear as a (self) sable, not a sable steel or anything. ch + Ed would appear as a (self based) pointed white. The C and E genes don't really interact anything special, not like A and E. E helps decide where the pigments go, and C just turns off (or lightens) the pigment. Like in an ermine: the non extension gene would turn the rabbit into an orange and the cchd would strip the orange of its orange pigment, leaving it nearly white. In almost any case, if you had a rabbit that was dominant black you could replace its pattern with self (aa) and it's extension with full extension (E_) to estimate what color it would be. If you were more interested in the interaction of the A + E series I would check out some of the research by L Fontanesi

 

[user 7388]

Thanks. Sounds like I've still got some reading to do.

 

[hotzcatz]

I really hope they come up with a different name for it! With a name like 'Dominant Black' I would usually associate that with just a mere B.

How common is it? I've never heard of it before?

 

[user 7388]

It's also sometimes called "black agouti," "dark extension," "dark steel" ... I think it's pretty rare still so the naming is a little all over the place. You only see it in some literature about the E locus.

Edit: I'm reading the Handbook on Genetics Vol 4 chapter on rabbits where they call Ed "dominant extension" and that's probably the most correct name for it. I'll be using that moving forward