Question

Two guinea pigs, both with the genotype AaBb, produce a large number of offspring. The A gene codes for the presence of white coat color with the dominant "A" allele coding for bright white fur and the recessive "a" allele is unable to produce any protein. The B gene codes for coat color with the dominant "B" allele coding for black fur and the recessive "b" allele coding for brown fur. If the dominant "A" allele is present it masks the effect of the dominant "B" genotype (i.e. if 1 dominant A allele is present, B alleles will not be expressed even if present) . What phenotypic ratio do you expect to see in the offspring?

Answer 1

Answer:

Bright white fur 3/4

Black fur            3/16

brown fur           1/16

Explanation:

From the Punnet's square analysis (see the attached image);

• A_B_    9/16
• A_bb     3/16
• aaB_     3/16
• aabb      1/16

A_B_ and A_bb will always give offsprings with bright white fur since allele A always mask the effect of B.

aaB_ will always give offsprings with black fur since allele a does not produce any protein.

aabb will give offsprings with brown fur since b codes for brown fur colour.

Hence, the phenotypic ratio of the offspring will be;

Bright white fur 3/4

Black fur            3/16

brown fur           1/16