Mendel performed crosses involving two characters. They are called dihybrid crosses that made to study inheritance of two pairs of genes. The classical example of dihybrid cross given below is the use of two pairs of characters namely the seed colour and seed shape. The plants with yellow and round seeds (pure) were crossed with those having green and wrinkled seeds (pure). The F1 seeds were yellow and round. F1 plants were selfed and F2 seeds obtained which showed all the four possible combinations, i.e., (i) yellow and round seeds, (ii) yellow and wrinkled seeds, (iii) green and round seeds, and

(iv) green and wrinkled seeds in 9 : 3 : 3 : 1 ratio. It can be shown by the following cross.