Question

What were the four different varieties of pea plants obtained by Mendel in his dihybrid cross experiment? Show their ratio with the help of a checker board.

Answer 1

A dihybrid cross is a cross between F${}_1$ offspring of two individuals that differ in two traits of a particular interest. For example, Mendel took homozygous dominant Round and yellow seeds (RRYY) and crossed it with homozygous recessive wrinkled and green seeds (rryy), the progeny obtained in F${}_1$ generation were all round and yellow seed (RrYy). The offsprings were heterozygous for both R and Y gene. The F${}_1$ plant has four types of gametes, RY, Ry, rY, and ry. For genes on separate chromosomes, each allele pair shows independent assortment. Thus, by crossing F${}_1$, the phenotypic ratio was 9:3:3:1, where 9 is yellow and round seeds, 3 represents round and green seeds, 3 represents yellow and wrinkled seeds and 1 represents green and wrinkled seeds.