Question

In Labrador retrievers, black coat colour (B) is dominant to brown coat colour (b). A breeder has a black male that has won numerous awards and is assumed to be a purebred black coat. The breeder mates him with a brown female and 10 puppies are born. 2 of which are brown.. Identify and justify the genotype of the male dog. Support your answer with a punnett square.

Answer 1

The male Labrador retriever, although black, must have a Bb genotype based on the evidence of brown offspring. He is not purebred black (BB) as initially assumed, but rather, he carries the recessive brown gene (b).

Step-by-step explanation:

Given that the black coat color (B) is dominant in Labrador Retrievers and the brown coat color (b) is recessive. If the black male was a purebred with a genotype of BB, all offspring would be black regardless of the females' genotype. However, in this case, there are some brown offspring, supporting the conclusion that the male must not be a purebred black coat (BB), but rather a hybrid with one dominant and one recessive gene (Bb). Consequently, the male's genotype must be Bb.

Here's how: the brown female Labrador is bb (since brown is recessive and she has a brown coat), and if the male is Bb, when you use a Punnett square to cross Bb by bb, you have an equal chance (50 percent) of getting black (Bb) or brown (bb) offspring. This result is compatible with the provided data where 2 out of 10 puppies (20 percent - not far from the theoretical 50 percent due to the randomness of inheritance) have a brown coat.

Learn more about Genotype determination