(a) Mendel carried out a Monohybrid cross. He crossed pure bred (homozygous) tall pea plants (TT) with pure bred , Homozyzous dwarf pea plants (tt) and found that only tall pea plants were produced in the first generation and there were no dwarf pea plants.

He concluded that the first generation showed the traits of only one of the parent plant with the trait for tallness. The trait of the other parent plant—dwarfness— did not show up in the progeny of the first generation.

He then crossed the tall pea plants obtained in the first generation (F1 generation) and found that both tall plants and dwarf plants were obtained in the second generation (F2 generation) in the ratio of 3:1. Mendel noted that the dwarf trait of the parent pea plant which disappeared in the first generation progeny reappeared in the second generation.

Thus Mendel concluded that the trait for Tallness (T) was dominant over the trait for dwarfness (t). The recessive trait was not able to express itself in the heterozygous condition like in the F1 generation. However, it was able to express itself in the homozygous condition like that in the f2 generation.

In this way, Mendel’s experiments with tall and dwarf pea plants showed that the traits may be dominant and recessive.

(b) Mendel performed an experiments in which he took a tall plant with round seeds and a short plant with wrinkled-seeds. In F1, all plants were tall and had round seeds. Tallness and round seeds were thus dominant traits. When these these F1 progeny  were crossed to generate F2 progeny it was found that some F2 progeny were tall plants with round seeds, and some were short plants with wrinkled seeds. At the same time there were new combinations besides the parental ones which were tall but had wrinkled seeds, while others were short, but had round seeds. Thus, Mendel’s experiments showed that the tall/short trait and the round seed/wrinkled seed trait are independently inherited.