Question

8.In a variety of beans the genes for pod texture and seed color are closely linked on the same chromosome. Tough pods (T) are dominant to tender pods (t), and red seeds (R) are dominant to (r) green seeds. Two true breeding strains are crossed: one has tough pods and red seeds, and the other has tender pods and green seeds. The resulting F1 were the self-crossed to produce an F2 generation.

a. What are the genotypes and phenotypes of the F1 generation?

b. What proportion of the F2 generation will have tender pods?

c. What proportion of the F2 generation will have red seeds?

d. What proportion of the F2 generation will have tender pods AND red seeds?

Answer 1

a) Genotypes & Phenotypes in F1 generation

TtRr, Tough and Red seeds

b) Tender pods

Genotypes - ttRR (1), ttRr(2), ttrr (1)

Proportion will be 3/16

c) Red seeds

Genotypes - TTRR, TTRr (2), TtRR (2), TtRr (4)

Proportion will be 9/16

d) Tender pods & red seeds

Proportion will be 3/16

Step-by-step explanation:

Tough pods (T) are dominant to tender pods (t)

Red seeds (R) are dominant to (r) green seeds

True breeding species

a) Tough pods and red seeds - TTRR

b) Tender pods and green seeds - ttrr

F1 generation -

TTRR * ttrr

TtRr

All the offspring will have TtRr genotype. The Phenotype of all offspring will be tough and red seeds.

F2 generations -

Self crossing the F1 generation species, we get -

TtRr * TtRr

Gametes - TR, Tr, tR , tr

TR Tr tR tr

TR TTRR TTRr TtRR TtRr

Tr TTRr TTrr TtRr Ttrr

tR TtRR TtRr ttRR ttRr

tr TtRr Ttrr ttRr ttrr

a) Genotypes & Phenotypes in F1 generation

TtRr, Tough and Red seeds

b) Tender pods

Genotypes - ttRR (1), ttRr(2), ttrr (1)

Proportion will be 3/16

c) Red seeds

Genotypes - TTRR, TTRr (2), TtRR (2), TtRr (4)

Proportion will be 9/16

d) Tender pods & red seeds

Proportion will be 3/16