A male flying tree squirrel with a medium-length tail has babies with a female with a medium-length tail. Over the years their total offspring number is 52. 13 of these babies have long tails, 27 have medium-length tails and 12 have short tails. a) Propose a method of inheritance for tail length. b) What is the likely genotype of the parents? c) What is the expected phenotypic ratio? d) Given the number of offspring that were had, what is the expected number of offspring for each phenotype?

Explanation:

(a) The mode of inheritance for the tail length would be incomplete dominance. In this type of inheritance, one of the alleles representing a gene in heterozygous conditions exert incomplete dominance on the other allele giving rise to a new phenotype.

(b) The likely genotype of the parents are heterozygous. The medium tail length results from the incomplete dominance of the long tail allele on the short tail allele. There is no allele for the medium tail length itself.

(c) Assuming that the allele for long tail length is T and that of short tail length is t, the genotype of the parents would Tt. Crossing the two parents

      Tt     x     Tt

  TT    Tt    Tt    tt

TT - Long tail = 1/4

Tt - medium tail = 1/2

tt - short tail = 1/4

(d) From the expected phenotype ratio

Expected number of offspring with long tail = 1/4 x 52 = 13

Expected number of offspring with medium tail = 1/2 x 52 = 26

Expected number of offspring with short tail = 1/4 x 52 = 13