Mendel discovered the fundamental laws of inheritance through his work on pea plants. He used around seven plant traits of which, length of the stem was also considered and hybridization between the tall plants (TT) and the dwarf plants (tt) was conducted.
Alleles refers to the alternative forms of a gene. They are the recessive and the dominant alleles. According to Medel's law of dominance, the recessive alleles are masked by the dominant alleles. In pea plants, the allele for tallness is dominant. It expresses itself in both the homozygous dominant condition and the heterozygous dominant condition. Thus, the possible genotypes of a tall pea plant are TT and Tt.