Question

A pet store has two guinea pigs. One has white fur and one has black fur. The white guinea pig has two recessive alleles for fur color (bb). The black guinea pig has one dominant allele (B) and one recessive allele (b) for fur color. What will most likely be the phenotypes ofcthe offspring on a cross between the two guinea pigs? Explain your answer. If you wish, you may also construct a punnett square showing the cross.

Answer 1

Given two guinea pigs with genotypes Bb and bb.

We use a Punnett square to show the possible phenotypes.

       B      b
b    Bb   bb
b    Bb   bb

So there are two possible phenotypes, Black fur (heterozygous) and white fur (heterozygous recessive).

Answer 2

Answer:

The offsprings will be black-furred and white-furred in a ratio 1:1

Explanation:

This cross involves a single gene coding for fur colour in guinea pig. According to the illustration in the question that the white-furred parent has two recessive alleles (bb) and the black-furred parent has a Bb genotype, the allele for black fur (B) is dominant over the allele for white fur (b) i.e. black fur will mask the expression of white fur in a heterozygous state.

In a cross between a bb and Bb genotype, the alleles segregate into gametes according to Mendel and four possible offsprings will be produced with two having a Bb genotype (phenotypically black-furred) and the other two having a bb genotype (phenotypically white-furred). Hence, the phenotypic ratio will be 1:1.