If there are 80 individuals in the f2 generation of a dihybrid cross involving duplicate genes, what would be the expected number of the dominant phenotype?

The correct answer is 45.

A dihybrid cross is a mating experiment between two organisms that are identically hybrid for two traits.

In F1 generation all of the offspring will be heterozygous. In F2 generation the phenotype ratio will be 9:3:3:1. 9 represents the ratio for dominant phenotype.

If there is 80 individuals than:

80 / (9+3+3+1) = 5

5*9=45