A pea plant which is homozygous for green pods which are inflated [GGII] is crossed with a homozygous plant for yellow pods which are constricted [ggii]. Answer the following questions:
Write the phenotypic ratio of the F2 generation.
Topic: Dihybrid F2 phenotypic ratio
Answer
9 : 3 : 3 : 1
9 Green, inflated pods 3 Green, constricted pods 3 Yellow, inflated pods 1 Yellow, constricted pod
9:3:3:1 is the standard DIHYBRID ratio. Write out WHAT each number refers to, since the question asks for the PHENOTYPIC ratio and the phenotypes are the answer.
The order is always: both dominant (9), first dominant with second recessive (3), first recessive with second dominant (3), both recessive (1).
NOTE THE TWO NEW COMBINATIONS — green with CONSTRICTED pods, and yellow with INFLATED pods. Neither appeared in the parents, and their appearance is the PROOF of INDEPENDENT ASSORTMENT: pod colour and pod shape were inherited independently of each other.
Compare the MONOHYBRID ratio 3:1, which applies when only one character is followed.