With independent assortment, the ratio of phenotypes in the F₂ generation of a cross between true-breeding strains (AA bb × aa BB) can be described as 9:3:3:1 when A and B are dominant over a and b. To what phenotype do the "3"s in the ratio refer? A)recessive for both traits B)dominant for the A trait and recessive for the B trait C)dominant for one trait and recessive for the other D)dominant for both traits

Question

Quizplus · Accepted Answer

The "3"s in the ratio refer to individuals that are dominant for one trait (either A or B) and recessive for the other trait (either a or b). This is because in the offspring of the cross between AA bb and aa BB, all individuals are heterozygous for both traits (Aa Bb). When these individuals undergo independent assortment, there are four possible gametes that can be produced with equal frequency: AB, Ab, aB, and ab. Therefore, in the F₂ generation, the ratio of phenotypes is 9 dominant for both traits : 3 dominant for one trait and recessive for the other : 3 recessive for one trait and dominant for the other : 1 recessive for both traits.

With Independent Assortment, the Ratio of Phenotypes in the F2

With Independent Assortment, the Ratio of Phenotypes in the F₂