Question

A mendelian experiment consisted of breeding tall pea plants cross breed with dwarf pea plants.
A. What is the expected height of plants in ${F_1}$ generation?
B. What will be the percentage of plants which are dwarfed in ${F_2}$ generation when ${F_1}$ plants are selfed?
C. State the expected ratio of genotype TT and Tt in ${F_2}$ progeny.

Answer 1

Hint: Mendel was the scientist who explored inheritance in pea plants. Mendel utilized the word “dominant” for the expression of tallness trait in pea plants (or those which are dominated in the ${F_1}$​ generation) and “recessive” for the expression of dwarfness trait in pea plants (or for the character that is hidden in the ${F_1}$ generation).

Complete answer:
When Mendel crossed a true-breeding tall pea plant (female parent) with a true-breeding dwarf pea plant, he received tall offsprings similar to one of the parents in the first filial generation and assigned as ${F_1}$​. Therefore, in the case of ${F_1}$ generation, all plants are tall.
Self-fertilization among the hybrids of the first filial generation gave rise to the second filial generation, comprising of 1064 plants, out of which 787 plants were tall and 277 plants were dwarf i.e. tall and dwarf plants from the ${F_1}$ generation were present in ratio of 2: 1 :1, which is approximately equivalent to 3:1. Hence, about 25 percent of dwarf plants were obtained.

In the first filial generation, TT X Tt cross will provide offsprings of 50 percent of TT and 50 percent of Tt. In the second filial generation, when they are self-crossed, the gametes will be T from TT and T and t from Tt. In this way, the genotype will be 1:1 as half homozygous tall and half heterozygous tall.

So, the ratio of both TT and Tt is 50 percent individually.

Note:
Gregor Mendel, in between 1856-1863, started performing hybridization experiments on pea plants and in 1866, he published his experiment on plant hybridization. The scientific name of a pea plant is Pisum sativum. Mendel proposed three laws of inheritance namely: Law of Dominance, Law of Segregation and the Law of Independent Assortment.