(a) The cross was made between round, green seeds and wrinkled, yellow seeds. In the given cross, two traits were taken into account, which is a dihybrid cross. Yellow colour and round shape is dominant over green colour and wrinkled shape. The above cross shows round and yellow seeds in the F1 generation. It occurs because dominant traits (round and yellow) express itself, whereas recessive traits (wrinkled and green) get suppressed.
(b) On selfing of F1 generation: Phenotypic ratio − 9:3:3:1 Round yellow − 9 Round green − 3 Wrinkled yellow − 3 Wrinkled green −1