If you don't mind me jumping in!
This is a pretty diagram that shows what dogs that appear to be a particular color can carry as a recessive.
FIGURE 1.
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Snagged from Wing-N-Wave Labradors Genetics
Thanks, that's very interesting. Now, a quick question. What about mixed litters where there are yellow, chocolate and black labs in the same litter even if both parents are say, black labs. How does that happen? I've always wondered.
Here's the basic idea: there are really only TWO colors of Labrador - Black and Chocolate. That's the color they are underneath, i.e. their skin. Chocolate is recessive, so a Black Lab can carry a Chocolate gene.
Yellow Labs result when the gene for pigment in the coat color is absent. There are two possible kinds of Yellow Labs - a Black Lab with a yellow coat, and a Chocolate Lab with a yellow coat. The Yellow Labs with chocolate skin are known as "Dudleys" - those are the ones with pink noses. They are barred from the show ring and breeders try to avoid breeding them (another reason why the Choc gene pool is more restricted). The gene for yellow coat pigment is also recessive.
So Dozer (whose dad was a Yellow Lab) may give the black skin or the chocolate skin to his offspring, and he may also give the gene for a yellow coat. When he was bred to a Chocolate, Shelley's mom, all nine of the pups were either black or chocolate - no yellows. If he were bred to a proper (black skinned) yellow Lab, there wouldn't be any Dudleys (but the pups would have the possibility of carrying one copy of the chocolate gene). If he were bred to a bitch with a chocolate gene AND a yellow gene, you would have the possibility of all three colors in the litter (and of a Dudley or two).
Occasionally you can have a yellow-to-yellow mating (which should produce all yellows) with a black pup cropping up. It's pretty rare, and some theorize that some yellow Labs aren't "really" yellow, but are carrying a secondary gene that may be expressed as black. More than you ever wanted to read about coat color in Labs
I can work the permutations for Siamese cats in my head, because (a) I bred them for 15 years and (b) there are only TWO combinations in the classic Siamese colors - (1) Blue or Seal; (2) Dilute factor, which gives Lilac or Chocolate. But the third factor in the Labs means that I would have to work out the probabilities on paper! Argh!
If you don't mind me jumping in!
This is a pretty diagram that shows what dogs that appear to be a particular color can carry as a recessive.
=ororor
=oror
=or
Snagged from Wing-N-Wave Labradors Genetics