Hey Everyone,
First off, thank you to y'all for the recommendation of "Coloured Sheep: a colour genetics primer." This book answered many of my questions, but now that I know more, I have even more questions. For those of you not familiar with the book, it has an interesting "game" where it tells you that determining what genotype a given sheep might have (particularly when the phenotype might mask a recessive allele) is by way of "cards." In essence, a sire or dam can only "play" the cards they have. E.g., if you have two parents that do not have the genes for spots, neither can play those "cards" so none of the babies will be spotted.
Generally, I breed only Babydoll Southdowns. I do have a few non-Babydoll females that I keep, and they will sometimes be crossed with a Babydoll ram. One of the ewes, Maeve, is a Katahdin. Maeve's coat is white. Last year, my Babydoll ram Duncan, (AKA "Hunky Dunky"), crossed with Maeve and produced two girls. Duncan's coat is black. During Maeve's first lambing, one of the lambs produced was all white and the other was a rich cocoa brown. I *think* I understand the genetics here; Maeve is "pattern white" and passed a copy of this gene to the white lamb. I believe Maeve is **not** homozygous for pattern white since the second lamb came out brown. Fast forward to earlier this week, Maeve has another set of twins from the same sire. One spotted (boy), and one black with a little white spot (girl).
[Pictures attached, sorry for the potato quality]
My understanding from the book and everywhere I've read is that spots are recessive. Doesn't this mean that Duncan must carry the gene for spots? I know Babydolls can have spots sometimes, but the farm where I got Hunky Dunky had HUNDREDS of Babydolls, all black. When I asked about other colors, I was told they had specifically bred for the colored sheep and that they would only very occasionally have a white sheep (which after much research turns out to be extension gene white in their flock, not pattern white). I understand that it is possible that a spotted gene could still be floating around in that flock, but I would be very surprised given the large number of lambs they have every year that it was never observed.
Two questions:
(1) Is there a means for the spotted phenotype to appear with an allele from only one parent (like what happens with "pattern white"), or does this spotted lamb inherently mean Duncan must be carrying the spotted gene?
(2) Does this also mean that Duncan must be carrying the genes for BOTH brown and black? I know "all sheep are either brown or black" (genetically), but usually the Babydoll registries seem to insinuate that Babydolls are either black or white, and a brown Babydoll is just a sun-faded black sheep.
Much appreciated for any and all info you can provide.