Question

Assuming complete dominance will occur, the offspring of the cross AA × Aa will show a phenotypic ratio of ______.

Options

• 3 : 1

• 1 : 2 : 1

• 9 : 3 : 3 : 1

• 9 : 1

Answer 1

Assuming complete dominance will occur, the offspring of the cross AA × Aa will show a phenotypic ratio of 3 : 1.

Explanation:

The genotype AA crossed with Aa will produce offspring genotypes of 50% AA and 50% Aa. Both genotypes show the dominant phenotype because A is completely dominant. Hence, there is no ratio of different phenotypes; all offspring show the dominant trait. So the phenotypic ratio is effectively 100% dominant phenotype, sometimes described as 1 (dominant) : 0 (recessive), but in the context of multiple-choice answers, this corresponds to a uniform phenotype rather than ratios like 3:1, indicating all dominant phenotype. The standard phenotypic ratio 3:1 or 1:2:1 applies for crosses like Aa × Aa, not AA × Aa.