Answer to Question #191232 in Biology for Amanda

Question

1.     In house cats, the polydactyl trait (more than five digits on paws) is dominant to having five digits (recessive trait). A five-digit female cat was mated to a male of unknown genotype/phenotype. They had nine offspring; five of the offspring were polydactyl, while the other four had five digits.

 

a.     From the information above, clearly indicate what the genotypes of each of the parents are. (2 marks)

 

 

 

 

b.     Draw a Punnett square for this cross and indicate the genotypic and phenotypic percentages of the offspring. (2 marks)

 

 

 

 

 

c.      If two of the polydactyl F1 offspring were crossed, what would be the expected genotypic and phenotypic percentages of this F2 generation of offspring? Draw the Punnett square for this mating. (3 marks)

Answer 1

Assume that p - recessive allele, P - dominant allele.

a. A genotype of a five-digit female cat is pp (homozygous recessive). Since the offspring included five-digit and polydactyl individuals, a male parent has a genotype Pp (heterozygous).

b. A Punnett square of the cross is as follows:

From here, phenotypic percentages are 50% five-digit cats and 50% polydactyl cats.

Genotypic percentages are 50% homozygous recessive (pp) and 50% heterozygous (Pp).

c. A Punnett square of the F2 cross:

From here, phenotypic percentages are 75% polydactyl cats and 25% five-digit cats.

Genotypic percentages are 25% homozygous dominant (PP), 50% heterozygous (Pp) and 25% homozygous recessive (pp).