Which phenotypic ratio is likely to occur in crosses of two completely dominant,independently segregating gene pairs when both parents are fully heterozygous?
A)2:4:6:8
B)3:2:3:1
C)3:1
D)1:1:1:1
E)9:3:3:1

Question

Quizplus · Accepted Answer

When both parents are fully heterozygous, the genotype of each parent is AaBb, with A and B being completely dominant gene pairs. In this case, the possible gametes produced by each parent are AB, Ab, aB, and ab. When these gametes are combined, the resulting offspring can have any of the following genotypes: AABB, AABb, AaBB, AaBb, AAbb, aaBB, aaBb, or aabb. The ratio of these genotypes can be determined using a Punnett square, which results in a 9:3:3:1 phenotypic ratio. Therefore, the best choice is E.

Which Phenotypic Ratio Is Likely to Occur in Crosses of Two