MP Board · Class 10 · Science · Heredity and EvolutionExplain Gregor Johann Mendel's monohybrid cross experiment with the help of a suitable checkerboard (Punnett square). What conclusions were drawn from this experiment regarding inheritance of traits?

Introduction to Mendel's Monohybrid Cross\nGregor Johann Mendel, known as the father of genetics, performed hybridization experiments on garden peas (Pisum sativum). A monohybrid cross involves the crossing of two parent plants differing in a single pair of contrasting characters.

Experimental Details

• Parents (P generation): Mendel crossed a pure breeding tall pea plant with a pure breeding dwarf pea plant.
• First Filial Generation (F1 generation): All plants obtained in the F1 generation were tall. The trait for dwarfness did not appear at all in this generation.
• Self-Pollination (F2 generation): Mendel then allowed the F1 tall plants to self-pollinate. In the F2 generation, both tall and dwarf plants appeared in a approximate 3:1 ratio.

Explanation Using Punnett Square\nLet the allele for tallness be represented by T (dominant) and the allele for dwarfness by t (recessive).

• Parent genotypes: TT (tall) × tt (dwarf)
• F1 generation genotype: Tt (all tall)
• F2 Punnett Square for Tt × Tt:

  	T	t
  T	TT	Tt
  t	Tt	tt

• Genotypic Ratio in F2: 1 (TT) : 2 (Tt) : 1 (tt)
• Phenotypic Ratio in F2: 3 Tall : 1 Dwarf

Conclusions Drawn

1. Law of Dominance: Out of a pair of contrasting characters interacting together, only one is able to express itself while the other remains suppressed. The one that expresses is the dominant character, and the one that is suppressed is the recessive character.
2. Law of Segregation (Law of Purity of Gametes): The alleles do not show any blending and that both the characters are recovered as such in the F2 generation though one of these is not seen at the F1 stage. During gamete formation, the factors or alleles of a pair segregate from each other such that a gamete receives only one of the two factors.