Question

Why do we get 9:3:3:1 ratio in $F_2$ of Dihybrid cross instead of the expected 3:1 ration for yellow round and green wrinkled respectively?

Answer 1

• The P parental cross is between true-breeding lines of wrinkled yellow peas and round green peas That is the chance of getting an R allele and a Y allele is 50% of getting an R.
  
• Then, we expect a characteristic 9:3:3:1 phenotypic ratio