Hey All AIPMT Biology Aspirants, read about MENDEL’s Dihybrid Cross and Law of Independent Assortment in this study material of AIPMT.

In monohybrid cross, Mendel used plants that differ in only one characteristic. After monohybrid cross, Mendel also performed experiments with plants that differ in two contrasting characters. This cross is called as Dihybrid Cross.He crossed plants of Round, Yellow seeds with plants of Wrinkled, Green seeds.

• Round seed shape and yellow seed color are dominant characters over wrinkled and green seeds.
• All the F1 progeny came out to be Round and Yellow seeds.
• On selfing of F1 plants four phenotypic classes were observed in the F2, represented by two parental and two new combinations.
• Two parental classes are Round, yellow seeds and Wrinkled, green seeds. Two new combination formed are Round, green seeds and Wrinkled, yellow seeds.

These four classes formed in ratio of 9 Round yellow: 3 Round green: 3 Wrinkled yellow: 1 Wrinkled green, out of total 16 types of seeds.

Mendel’s Dihybrid Cross

Genotypic ratio of Dihybrid Cross

Law of Independent Assortment

• Based upon observations of dihybrid cross, Mendel proposed Law of Independent Assortment. The law states that ‘when two pairs of traits are combined in a hybrid, segregation of one pair of characters is independent of the other pair of characters’.
• OR, Genes encoding different characteristics separate independently of one another during gamete formation.
• That is, round, yellow and wrinkled green traits of parental generation assort independently during gamete formation, so we observed 2 new combinations of hybrid in F2 generation as, round, green seeds and wrinkled, yellow seeds.