Question

Dihybrid test cross involves crossing of F1 dihybrid to

• A. double recessive parent
• B. double heterozygous dominant parent
• C. both a and c
• D. homozygous dominant parent

Answer 1

The correct option is A double recessive parent

Dihybrid test cross involves crossing of F1 dihybrid to double recessive parent.
Dihybrid test cross: YyRr X yyrr
Where , YyRr is yellow round seeds and yyrr is green wrinkled seeds.
The gametes formed are : YR, Yr, yR,yr
Thus when a F1 dihybrid (YyRr) is crossed with a double recessive parent (yyrr), the offsprings obtained in the test cross is as follows:


$\begin{array}{ccccc}& \text{YR}& \text{Yr}& \text{yR}& \text{yr}\\ \text{yr}& \text{YyRr}& \text{Yyrr}& \text{yyRr}& \text{yyrr}\\ & \text{(Yellow, round seeds)}& \text{(Yellow, wrinkled seeds)}& \text{(Green, round seeds)}& \text{(Green, wrinkled seeds)}\end{array}$
Hence, the dihybrid test cross ratio is
YyRr : Yyrr : yyRr : yyrr = 1 : 1 : 1 : 1.