Question

How many different genotypes and phenotypes are produced in the F2 generation of a dihybrid cross performed by Mendel considering that the parents are true breeding for round, yellow seeds and wrinkled, green seeds?

• A. 4 - phenotypes
  9 - genotypes
• B. 4 - phenotypes
  16 - genotypes
• C. 16- phenotypes
  16 - genotypes
• D. 4 - genotypes
  9 - phenotypes

Answer 1

The correct option is A 4 - phenotypes

9 - genotypes
Considering the parents to be pureline of contrasting traits of seed shape and seed colour:
F2 generation:
$\begin{array}{ccccc}\text{Gametes}& \text{RY}& \text{Ry}& \text{rY}& \text{ry}\\ \text{RY}& \text{RRYY}& \text{RRYy}& \text{RrYY}& \text{RrYy}\\ & \text{(Round, yellow)}& \text{(Round, yellow)}& \text{(Round, yellow)}& \text{(Round, yellow)}\\ \text{Ry}& \text{RRYy}& \text{RRyy}& \text{RrYy}& \text{Rryy}\\ & \text{(Round, yellow)}& \text{(Round, green)}& \text{(Round, yellow)}& \text{(Round, green)}\\ \text{rY}& \text{RrYY}& \text{RrYy}& \text{rrYY}& \text{rrYy}\\ & \text{(Round, yellow)}& \text{(Round, yellow)}& \text{(Wrinkled, yellow)}& \text{(Wrinkled, Yellow)}\\ \text{ry}& \text{RrYy}& \text{RrYy}& \text{rrYY}& \text{rrYy}\\ & \text{(Round, yellow)}& \text{(Round, green)}& \text{(Wrinkled, yellow)}& \text{(Wrinkled, green)}\end{array}$
This will lead to the production of following phenotypes and genotypes:-
Phenotypes:- 4 types
Round yellow : round green : wrinkled yellow : wrinkled green
= 9 : 3 : 3 : 1
$\begin{array}{cc}\text{Phenotypes}& \text{No.of offsprings}\\ \text{Round yellow}& \text{9}\\ \text{Round green}& \text{3}\\ \text{Wrinkled yellow}& \text{3}\\ \text{Wrinkled green}& \text{1}\end{array}$
Genotypes:- 9 types
RRYY : RrYY : rrYY : RRYy : RrYy : rrYy : RRyy : Rryy : rryy
= 1 : 2 : 1 : 2 : 4 : 2 : 1 : 2 : 1
$\begin{array}{cc}\text{Genotypes}& \text{No.of offsprings}\\ \text{RRYY}& \text{1}\\ \text{RrYY}& \text{2}\\ \text{rrYY}& \text{1}\\ \text{RRYy}& \text{2}\\ \text{RrYy}& \text{4}\\ \text{rrYy}& \text{2}\\ \text{RRyy}& \text{1}\\ \text{Rryy}& \text{2}\\ \text{rryy}& \text{1}\end{array}$