CBSE · Class 10 · Science · HeredityExplain Mendel's Dihybrid Cross with the help of a checker board. State the law derived from this cross and give the final phenotypic ratio.

Introduction to Dihybrid Cross\nA dihybrid cross is a breeding experiment that tracks the inheritance of two pairs of contrasting traits simultaneously. Mendel crossed pea plants with round, yellow seeds ($RRYY$) and wrinkled, green seeds ($rryy$).

Experimental Procedure

1. Parental Generation: Pure round yellow ($RRYY$) $\times$ Pure wrinkled green ($rryy$).
2. $F_1$ Generation: All offspring were round and yellow with genotype $RrYy$, showing that round and yellow are dominant traits.
3. $F_2$ Generation: Self-pollination of $F_1$ plants ($RrYy \times RrYy$) produced four types of gametes ($RY, Ry, rY, ry$).

Punnett Square for Dihybrid Cross

Phenotypic Ratio in $F_2$

• Round Yellow: 9
• Round Green: 3
• Wrinkled Yellow: 3
• Wrinkled Green: 1
• Ratio: $9:3:3:1$

Law of Independent Assortment\nBased on this cross, Mendel formulated the Law of Independent Assortment, which 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 during gamete formation.