It is possible because there are two different mutations that can cause chocolate. I have the research paper, courtesy of Maureen Gamble, on my computer in my office( I'm at home right now) and can send it to you if you're interested. It's a paper from the primary literature, might be hard slogging if you don't speak molecular biology.
Be the one to stick my head up and say NOT possible. I have bred chocolates for close on 40 years and in all that time have never bred a black from 2 chocolates, and I have used a Varity of different lines. Even if both carry yellow the only thing you will get is a Dudley or 2.. Two recessive's can't produce a dominant and black is dominant in the Labrador. The only exception to that rule is mating a chocolate that doesn't carry yellow to a yellow that doesn't carry chocolate the whole litter will be black (c,y)
It is possible because there are two different mutations that can cause chocolate. I have the research paper, courtesy of Maureen Gamble, on my computer in my office( I'm at home right now) and can send it to you if you're interested. It's a paper from the primary literature, might be hard slogging if you don't speak molecular biology.
If you get an email from a stranger asking for the paper, it's just me. I am very interested in reading it. :)
I seem to recall someone getting a few blacks in an all chocolate litter a few years ago. They did DNA testing to prove parentage, and the chocolates were indeed the parents. It's rare but it can happen, I believe the paper that Maureen has explains it way better than I could.
In order to get black, one of the parents must carry the dominant"B" allele for black pigment. The chocolate parents in question are either EEbb or one may be Eebb (chocolate carrying yellow), but either way to be chocolate they have to have the dominant allele for the dark coat "E", however chocolates do not have black pigment and therefore carry the recessive "bb" alleles.
Whether or not Maureen stumbled on to some sort of mutation with the "E" allele overriding the "b" allele on pigment and allowing a black (E?B?) pup or two to be created, I suppose there is on a very, very rare occasion a slight possibility of something like that happening if DNA verifies it.
Please know that this is highly highly unlikely to occur. Any blacks in a litter from two chocolate parents (E?bb) should be very suspect of another sire and DNA testing MUST be done.
I sent Gail the paper. It was published in a refereed journal. The phenomenon is called complementation. It can occur because genes are very large pieces of DNA, and there can be different mutations carried by different lines. Apparently the proteins produced by two of these mutations can complement so that you get a functional enzyme to produce melanin. Several mutations of the B locus exist in Labradors, possibly because the color was introduced from more than one source. Yes, it would be very rare.
As far as I know, after breeding chocolates for a good number of years, I have never see this happen. It's a rarity at best. I heard of 1 supposed case in 25 years.
The multiple or different stud-dog theory sounds likely.
If it were my litter, I would DNA test the puppies but I am not telling you how to spend your money.
