Question

In rats, the allele for pigmentation (P) is dominant to the allele for albinism (p). The B gene allele for black pigmentation (B) is dominant to the allele for cream pigmentation (b). The pp homozygous recessive genotype is epistatic to any allele combination at gene B.

a. Predict the genotypes of the F1 progeny of a cross between a pure-breeding black rat and an albino rat that is also homozygous for the allele for cream pigmentation.

b.Predict the phenotypes of the F1 progeny of a cross between a pure-breeding black rat and an albino rat that is also homozygous for the allele for cream pigmentation.

c.Predict the phenotypic ratio of the F2 progeny of a parental cross between a pure-breeding black rat and an albino rat that is also homozygous for the allele for cream pigmentation.

Answer 1

a. F1 genotype PpBb

b. F1 phenotype All black offsprings

c. F2 phenotypic ratio: Black 9/16 cream 3/16 albino 4/16

Step-by-step explanation:

In rats, the allele for pigmentation (P) is dominant to the allele for albinism (p).

The B gene allele for black pigmentation (B) is dominant to the allele for cream pigmentation (b).

cross 1

pure breeding black rat x albino rat homozygous for cream

parent PPBB x ppbb

a. F1 genotype PpBb

b. F1 phenotype All black offsprings

PpBb x PpBb

c. F2 phenotypic ratio: Black 9/16 cream 3/16 albino 4/16