Answer:
Genotype: Bb (heterozygous)
Phenotype: brown fur
Explanation:
Since allele B is dominant to allele b, as long as genotype has allele B in it, its effect of phenotype will be expressed instead, regardless of whether allele b is present.
As mouse genotype is stated as Bb, on the chromosome from its parents, allele B comes from one parent while allele b is inherited from the other parent.
Phenotype is the expressed trait. In this case, as genotype has allele B, the phenotype will be brown fur as its effect is expressed.
