Answer:
(BB) or (Bb)
Explanation:
Given that (B) allele , is responsible for fur that is dark brown, and (b) allele is responsible for fur color that is light brown, the dominant allele is (B) allele for dark brown fur. Dark brown fur allele would always express itself over the recessive allele, (b).
For a mouse that has dark brown fur, the possible genotype it could have is either (BB) => 2 dominant allele, or (Bb) => 1 dominant allele and a recessive allele. The dominant allele would always express itself even in the presence of the recessive allele.
