Mendel reported that he further tested his hypothesis of ind

Mendel reported that he further tested his hypothesis of independent assortment by planting F2 seeds from his seed shape and color dihybrid cross and scoring the F3 progeny. In one of these experiments, he planted 301 round, yellow F2 seeds, allowed the plants to self-fertilize and scored the F3 seeds produced by each plant. He observed 38 F2 plants which produced only round, yellow seeds, 65 F2 plants which produced all round seeds that segregated 3 yellow to 1 green, 60 F2 plants which produced all yellow seeds that segregated 3 round to 1 wrinkled, and 138 F2 plants which produced seeds in the 9:3:3:1 phenotypic ratio that he had previously observed with the F2 seeds.

Where I/i codes for seed color (I = yellow, i = green), and R/r codes for seed shape (R = Round, r = wrinkled)

What was the genotype of the F2 plants which produced all round F3 seeds that segregated 3 yellow to 1 green?

A. IIRR

B. IIRr

C. IiRR

D. IiRr

Under Mendel’s hypothesis of independent assortment, how many of the 301 F2 plants grown from round, yellow seeds are expected to produce F3 seeds showing a 9:3:3:1 phenotypic segregation ratio? Round your answer to the nearest whole number.

A. 35

B. 75

C. 134

D. 138

E. 151

F. 169

Solution

1. The genotype of the F2 plants which produced all round F3 seeds that segregated 3 yellow to 1 green will be IiRr

parents: IiRr x IiRr

gamets : IR,Ir,iR,ir & IR,Ir,iR,ir

IR Ir iR ir

  IR IIRR IIRr IiRR IIrR

Ir IIRr iirr IiRr Iirr

  iR IiRR IiRr iiRR iiRr

ir IiRr Iirr iiRr iirr

2. Total number of F2 plants = 301

Total number of platns producing only round, yellow seeds = 38

Total number of plants producing all round seeds = 65

Total number of plants producing all yellow seeds = 60

The expected plants to produce F3 seeds showing a 9:3:3:1 phenotypic segregation ratio

=301/2 = 150.5 = 151

So the ans is option E.151