Punnett Square & F₂ Generation — NEET Biology
✅ Asked in NEET 2021The Punnett Square shows the parental tall TT (male) and dwarf tt (female) plants, the gametes produced by them and, the F₁ Tt progeny. The F₁ plants of genotype Tt are self-pollinated. The symbols ♀ and ♂ are used to denote the female (eggs) and male (pollen) of the F₂ generation, respectively. The F₁ plant of the genotype Tt when self-pollinated, produces gametes of the genotype T and t in equal proportion. When fertilisation takes place, the pollen grains of genotype T have a 50 per cent chance to pollinate eggs of the genotype T, as well as of genotype t. Also pollen grains of genotype t have a 50 per cent chance of pollinating eggs of genotype T, as well as of
The Punnett Square predicts offspring genotypes when F₁ heterozygotes (Tt) self-pollinate. Each gamete has 50% chance of carrying T or t allele, so F₂ shows 1 TT : 2 Tt : 1 tt ratio (genotypic) and 3 tall : 1 dwarf (phenotypic). Students often confuse F₁ and F₂ generations or miscalculate gamete probabilities. Remember: equal proportions of gametes from heterozygote produce a 3:1 phenotypic ratio in F₂. This foundational concept tests understanding of segregation and probability in crosses—essential for predicting inheritance patterns in NEET genetics problems.
The production of gametes by the parents, formation of zygotes, the F₁ and F₂ plants, can be understood from a diagram called: (NEET 2021)
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