Dihybrid Crosses

In pea plants, Gregor Mendel also performed dihybrid crosses, breeding experiments between organisms that differ in two traits, such as seed shape and seed color.

For example, one plant is homozygous dominant for round and yellow seeds, while the other is homozygous recessive for wrinkled and green seeds.

When crossed, all plants in the F1 generation are dihybrids, meaning they are heterozygous for both genes.

The F1 plants display the dominant phenotype for both traits and produce round, yellow seeds.

When these plants self-fertilize, their progeny form the F2 generation.

This generation includes plants with round yellow, round green, wrinkled yellow, and wrinkled green seeds in a 9:3:3:1 ratio.

The ratio of round to wrinkled seeds and yellow to green seeds is 3:1 for each trait.

Because each trait retains its own 3:1 inheritance pattern, seed shape alleles are inherited independently of seed color alleles. This is known as the principle of independent assortment.