Question

I want to be clear that I'm not interested on just the correct awnser (I have the key), I am having trouble understanding the logic to which the awnsers were derived from.
Please explain why it is the correct awnser.

Thank you in adnvance.

A researcher finds two genes controlling flower color (W and R) that are 40 cM apart fromeach other on the same chromosome. They epistatically interact such that the flower color of W-R- is Red, W-rr is pink, wwR- is Red and wwrr is white. The researcher crosses a WWrr individual by awwRR individual to obtain an F1 that she then crosses to a wwrr individual. Figure out the resulting F2genotypic and phenotypic ratios on the other side of the paper and answer the following questions.For this section there is only one correct answer per question.

45. What fraction of the individuals from the test cross will have the wr/wr genotype?

A. 15%

B. 20%

C. 25%

D. 30%

E. 35%

46. What fraction of the individuals from the test cross will have the wR/wr genotype?

A. 15%

B. 20%

C. 25%

D. 30%

E. 35%

47. What fraction of the individuals from the test cross will be Red?

A. 10%

B. 20%

C. 30%

D. 40%

E. 50%

48. What fraction of the individuals from the test cross will be White?

A. 15%

B. 20%

C. 25%

D. 30%

E. 35%

49. What fraction of the individuals from the test cross will be Pink?

A. 15%

B. 20%

C. 25%

D. 30%

E. 35%

Answer 1

Parents: WWrr x wwRR
F1= WwRr
test cross: WwRr x wwrr

	WR (20%)	Wr (30%)	wR (30%)	wr (20%)
wr	WwRr (red)	Wwrr (pink)	wwRr (red)	wwrr (white)

45. What fraction of the individuals from the test cross will have the wr/wr genotype?

Answer: B. 20%

According to the given information, the genes are 40 cM apart. This means that the recombination frequency between W and R gene is 40%. The genotype WwRr would form a total of 40% recombinant gametes (20% WR and 20% wr) and 60 % non-recombinant gametes (30% Wr and 30% wR).

46. What fraction of the individuals from the test cross will have the wR/wr genotype?

Answer: D. 30%

The proportion of gamete with wR gene combination is 30%.

47. What fraction of the individuals from the test cross will be Red?

Answer: 50%

Solution: According to the given information, the presence of one copy of the "R" allele gives a red phenotype. Therefore, 50% of the progeny will have the red phenotype.

48. What fraction of the individuals from the test cross will be White?

Answer: B. 20%

Solution: The proportion of the gamete with wr genotype is 20%