Question

Which of the following statement(s) is /are correct regarding the Mendelian dihybrid cross?
A. The F2 phenotypic ratio is 9 : 3 : 3 : 1
B. Law of independent assortment can be explained on the basis of the dihybrid cross
C. F2 generation is obtained through the cross between F1 plants with one of the two parental plants
D. The gametes produced by F1 plants are of 4 types in 1:1:1:1 ratio.

• A. A, B, D
• B. A, C, D
• C. B, C, D
• D. A, B, C, D

Answer 1

The correct option is A A, B, D

Let’s analyse the statements using Mendel’s dihybrid cross in which two pea plants pureline for producing round, yellow seeds (RRYY) and wrinkled, green seeds (rryy) are crossed.
Gametes produced from F1 hybrids are in the ratio of 1: 1: 1: 1.
In Mendel's dihybrid cross, the F2 generation is obtained by selfing of F1 plants and not by crossing the F1 plants with one of the two parental plants.
In this example, F1 offspring RrYy after undergoing selfing produces F2 generation.
On F1 selfing, we have RrYy x RrYy
$\begin{array}{ccccc}\text{Gametes}& \text{RY}& \text{Ry}& \text{rY}& \text{ry}\\ \text{RY}& \text{RRYY}& \text{RRYy}& \text{RrYY}& \text{RrYy}\\ & \text{(Round, yellow)}& \text{(Round, yellow)}& \text{(Round, yellow)}& \text{(Round, yellow)}\\ \text{Ry}& \text{RRYy}& \text{RRyy}& \text{RrYy}& \text{Rryy}\\ & \text{(Round, yellow)}& \text{(Round, green)}& \text{(Round, yellow)}& \text{(Round, green)}\\ \text{rY}& \text{RrYY}& \text{RrYy}& \text{rrYY}& \text{rrYy}\\ & \text{(Round, yellow)}& \text{(Round, yellow)}& \text{(Wrinkled, yellow)}& \text{(Wrinkled, Yellow)}\end{array}$
The F2 phenotypic ratio is:-
yellow round : yellow wrinkled : green round : green wrinkled = 9 : 3 : 3 : 1.
Mendel’s dihybrid cross demonstrates independent assortment which states that the inheritance of one character (pair of traits) is independent of the other.