According to this law, when two factors of a character are unlike, one of them will manifest in the body and is called dominant while the other remains hidden and is termed recessive factor.

The law can be well explained by the monohybrid cross by studying the following crosses :

(i) Pure tall = TT, Hybrid tall = Tt

The 50% are pure tall and 50% hybrid tall. Then pure tall plants will produce 100% tall in F2 generation and hybrid plants will produce in ratio of 1 : 2 : 1 in the F2 generation.

(ii) When the cross is made between pure tall and pure dwarf, we get results as follows (Fig. 1.2)

Fig. 1.1. A Punnett square used to understand a typical monohybrid cross conducted by Mendel between true-breeding tall plants and true-breeding dwarf plants