Question

In complementary gene interactions, two genes work in tandem to produce a particular phenotype. Functional copies of both genes are required to produce the phenotype. What phenotypic ratios would be expected among the F2 progeny of a dihybrid cross involving dominant and recessive alleles for two such complementary genes?

A. 9:3:3:1
B. 9:7
C. 9:3:4
D. 15:1

Answer 1

B. 9:7

Step-by-step explanation:

In complementary gene interactions, the appearance of a particular phenotype requires the presence of a dominant allele in both genes. If one or both genes are homozygous recessive, then that phenotype will not appear.

In this case, all the individuals A_B_ will have a certain phenotype and individuals A_bb, aaB_ and aabb will have another phenotype.

The proportions 9 AB : 3 Ab : 3 aB : 1 ab become 9 AB : 7 not AB.