Give reasons for the appearance of new combination of characters in the F 2 progeny of the cross mentioned below. F 1 RrYy (Round, Yellow) X RrYy (Round, Yellow)

The given cross, i.e., RrYy x RrYy is a dihybrid cross with heterozygous genotypes. All the F 1 plants have round and yellow seeds. The characters of the F 2 progeny will be round yellow, round green, wrinkled yellow and wrinkled green in the ratio of 9:3:3:1. Since the genotype of both the parents is RrYy, the gametes produced will have RY, Ry, rY and ry genotypes. It shows that the alleles from the parental genotype assort independently into the gametes. Their chances of assortment do not depend on each other. This is called the principle of independent assortment, i.e., 3rd law of Mendelian genetics.