Question
Sat December 22, 2012 By:

what is the phenotypic and genotypic ratio of f1 generation in dyhbrid cross?also what is the genotypic ratio of F2 generation of dyhbrid cross?

Expert Reply
Sun December 23, 2012
The phenotypic ratio is 9:3:3:1 whereas the genotypic ratio is 1:2:1:2:4:2:1:2:1.
For example - In a cross between RRYY (round yellow seeds of pea plant) and rryy (green wrinkled seeds of pea plant), all F1 offspring would be RrYy i.e. Round yellow.
In F2 generation, we will get the following combination of gametes - RY Ry rY ry RY. When crossed, they would give the following possible offspring:
1 YYRR + 2 YYRr + 1 YYrr + 2YyRR + 4YyRr + 2 yyRR + 1yyRR + 2yyRr + 1yyrr
Thus the genotype ratio is 1:2:1:2:4:2:1:2:1.
 
The phenotype ratio is 9:3:3:1.  i.e. 9 round-yellow : 3 wrinkled-yellow : 3 round-green : 1 wrinkled-green pea seeds
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