Gregor Mendel performed numerous experiments using pea plants (Pisium sativum). He tested the height traits of pea plants by crossing tall pea plants (TT) and short pea plants (tt) to obtain offsprings that were all tall (Tt) in the first filial generation (F1).
This is possible because the allele for tallness is DOMINANT while the allele for shortness is RECESSIVE. This means that tallness allele (T) will mask the phenotypic expression of shortness allele (t) when in an heterozygous state (Tt) as in the F1 generation.
