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.

a. F1 genotype            PpBb

b. F1 phenotype   All black offsprings

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

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

lipid

explanation:

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