What is the genotypic ratio for the second filial generation in a dihybrid cross ?

Asked by Pranav Bang | 26th Jan, 2012, 04:26: PM

Expert Answer:

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)× rryy (green wrinkled seeds of pea plant), all F1 offspring would be RrYy.
In F2 generation, we will get the following combination,
 
   RY   Ry   rY   ry 
 RY 
RRYY RRYy RrYY RrYy
RRYy RRyy RrYy Rryy
RrYY RrYy rrYY rrYy
RrYy Rryy rrYy rryy
 Ry 
 rY 
 ry 
This would give the following possible offspring:

Possible
Offspring:

Genotype
Ratio

     

RRYY

1

     

RRYy

2

     

RRyy

1

     

RrYY

2

     

RrYy

4

     

Rryy

2

     

rrYY

1

     

rrYy

2

     

   rryy   

   1   

     

TOTAL

16

     
 

 Thus the genotype ratio is 1:2:1:2:4:2:1:2:1

Answered by  | 27th Jan, 2012, 09:12: AM

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