Question map
In pea, a pure tall plant (TT) is crossed with a short plant (tt). What will be the ratio of pure tall plants to short plants in the F2 generation ?
Explanation
In a Mendelian monohybrid cross, crossing a pure tall plant (TT) with a short plant (tt) produces an F1 generation that is entirely heterozygous (Tt). When these F1 plants self-pollinate (Tt x Tt), the F2 generation follows a specific genotypic ratio of 1:2:1. This ratio represents 1 homozygous dominant (TT), 2 heterozygous (Tt), and 1 homozygous recessive (tt). In this context, 'pure tall' refers to the homozygous dominant (TT) genotype, and 'short' refers to the homozygous recessive (tt) genotype. According to the genotypic ratio, there is 1 TT plant for every 1 tt plant in the F2 generation. Therefore, the ratio of pure tall plants (TT) to short plants (tt) is 1:1. This is distinct from the 3:1 phenotypic ratio, which groups TT and Tt together as tall.