Question

A species of mice can have long or short tails. if you crossed a male mouse which is heterozygous and has a long tail with a female mouse with a short tail, what would the expected phenotypic outcome be and why?

Answer 1

The expected outcome would be 50% of the time a long tail which is heterozygous (Pp) and 50% of the time a short tail which is recessive (pp).

Answer 2

The correct answer would be 1 (long tail): 1 (short tail).

Let us consider T and t be the dominant and recessive alleles of the gene responsible for the length of the tail respectively.

T codes for the long tails and t codes for short tails.

The genotype of one parent is a heterozygous long tail, that is, TT.

The genotype of other parent is a homozygous recessive short tail, that is, tt.

The cross would result in the production of offspring with two possible types of genotypes Tt and tt in the ration 2:2 that is, 1:1.

Thus, the phenotype ratio would also be 1 (tall tails): 1 (short tails).