AGB 121: Principles of Animal Genetics and Population Genetics (2+1)

DIHYBRID INHERITANCE

• Mendel crossed two varieties of pea plants which were differing in two pairs of contrasting characters.

 To view "Dihybrid Cross Animation"

• Trait 1 : Seed shape – Round and Wrinkled.
• Trait 2 : Seed colour – Yellow and Green.
• Round and Yellow (RRYY) are dominant over Wrinkled and Green (rryy) respectively.
• Mendel developed plants that were pure breeding for the two traits.
• When cross-pollinated, the offspring of such a cross were hybrids for two factors or genes, so they were called dihybrids.
• F1 generation was all heterozygous for round shape and yellow colour seeds (RrYy).
• When the F1 hybrids were allowed to self-pollinate, they produced four types of seeds in the ratio of 9: 3: 3:1 ( 9 round yellow: 3 round green: 3 wrinkled yellow : 1 wrinkled green ).
• In F₂ generation new combinations of genes were present - round green and wrinkled yellow. Neither parents had this trait combination.