What is the expected Punnett square ratio for a dihybrid cross?

In a dihybrid cross, which involves two traits and individuals that are heterozygous for both traits, the expected phenotypic ratio resulting from the offspring is indeed 9:3:3:1. This ratio emerges from the combination of the offspring's traits that arise from the independent assortment of the alleles for each trait.

To break it down, consider a classic example involving pea plants where one trait might be seed shape (round vs. wrinkled) and another trait could be seed color (yellow vs. green). When two dihybrid parents (both RrYy) are crossed, each parent can produce four types of gametes (RY, Ry, rY, and ry). The possible combinations of these gametes in the offspring result in:

• 9 individuals with round yellow seeds (R_Y_)

• 3 individuals with round green seeds (R_yy)

• 3 individuals with wrinkled yellow seeds (rrY_)

• 1 individual with wrinkled green seeds (rryy)

Thus, the resulting phenotypic ratio viewed from the offspring of such crosses is consistently 9:3:3:1. This ratio illustrates how alleles segregate independently during the formation