1-Mendel hypothesized that characters were carried as traits and an organism always carried a pair of factors for a character.
2-He also hypothesized that distinguishing traits of the same character were present in the population of an organism.
3-He also assumed that the traits shown by the pea plants must be in the seeds that produced them. The seeds must have obtained these traits from the parent plants.
Mendel crossed the pure bred ‘dwarf’ pea plants with pure-breed fall pea plants.
In F1 generation no dwarf pea plants were obtained in the first generation of progeny.
4- That means the first generation showed the traits of only one of the parent plants tallness. The trait of ‘dwarfness’ did’t show up in the progeny.
5-Then Mendel crossed the F1 generation plants and obtained three tall plants and one dwarf plant.
6-The dwarf trait of the parent plant which had seemingly disappeared in the first generation progeny, reappeared in the second generation.
7-Mendel named this trait as ‘recessive trait’ and the expressed trait of tallness as ‘dominant’.