Question
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What is the step-by-step process of a dihybrid cross?

Verified Answer

A dihybrid cross studies the inheritance of two different traits simultaneously, demonstrating how genes assort independently according to Mendel’s law of independent assortment.

Step-by-step process of a dihybrid cross:

1. Selection of parent generation (P generation)
Choose two pure-breeding parents with contrasting traits:
Example: Round Yellow seeds (RRYY) × Wrinkled Green seeds (rryy)

2. Formation of gametes
Each parent produces only one type of gamete:

  • RRYY → RY

  • rryy → ry

3. Fertilization (F₁ generation)
Gametes combine:

  • RY × ry → all offspring are RrYy

Result: All F₁ plants show dominant traits (Round Yellow)

4. Self-crossing of F₁ generation
F₁ plants (RrYy × RrYy) are crossed

5. Formation of gametes from F₁
Each F₁ plant produces four types of gametes due to independent assortment:

  • RY, Ry, rY, ry

6. Formation of F₂ generation (Punnett square 4×4):
16 possible combinations are formed

Phenotypic ratio:
9 Round Yellow : 3 Round Green : 3 Wrinkled Yellow : 1 Wrinkled Green

Genotypic combinations:
Include various combinations like RRYY, RrYy, rrYy, etc.

Conclusion:

  • Demonstrates independent assortment of genes

  • Shows how two traits are inherited together but independently

In simple terms: A dihybrid cross tracks the inheritance of two traits at once and shows how they combine in predictable ratios.