Fur color in mice is affected by a single gene. The gene for fur color has two alleles: B that causes dark brown fur, and b that causes light brown fur. In a mouse with dark brown fur, the genotype could be BB or:

The genotype could be BB or Bb

Explanation:

The genotype could be Bb which means it has heterozygous alleles.

The B which is allele for dark brown fur is dorminant and b for light brown is recessive. In this case, the dorminant allele masked the effect of the recessive allele b which make the dorminant allele B to be expressed phenotypically.

answer:

sequence 1- deletion

                  2- duplication

                  3- insertion

                  4- substitute

                  5- inversion