Dihybrid cross involves the inheritance of two pairs of contrasting characteristics(or contrasting traits) at the same time. The two pairs of contrasting haracteristics chosen by Mendel were shape and color of seeds: round-yellow seeds and wrinkled-green seeds.
Mendel crossed pea plants having round-yellow seeds with pea plants having wrinkled-green seeds. Mendel made the following observations:
(i) Mendel first crossed pure breeding pea plants having round-yellow seeds with pure breeding pea plants having wrinkled-green seeds and found that only round-yellow seeds were produced in the first generation `(F_(1))`. No wrinkled-green seeds were obtained in the `F_1`, generation. From this it was concluded that round shape and yellow color of the seeds were dominant traits over the wrinkled shape and green color of the seeds.
(ii) When the hybrids of `F_(1)` generation pea plants having rounds yellow seeds were cross - bred by self pollination then four types of seeds having different combination of shape and colour were obtained in second generation or `F_(2)` generation They were round yellow , round green , wrinkled - yellow and wrrinkled yellow and wrinkled - green seeds .
The ratio of each phenotype ( or appearence ) of seeds in the ` F_(2)` generation is 9:3:3:1 this is in known as the Dihybrid ratio .
Monohybrid cross is a genetic that involves a single pair of gene or trait .In this parents differ by single trait Eg. Height .
Dihybrid cross is a generatic cross that involves two pairs of genes , which are responsible for two trait . In this parents have two different independent trait. E.g flower colour , stem length .
