Use the following information to answer the next three questions: 1.) In corn pl

Question

Use the following information to answer the next three questions:

1.) In corn plants, a plant with a starchy endosperm (w) was mated to a yellow kerneled plant (p) with shrunken kernels (f). A wildtype individual from the F1 generation was then mated to a fully homozygous (mutant) individual. The following progeny were observed.

a) The gene order is P-F-W

b) The gene order is P-W-F

c) The gene order is W-P-F

2.) Using the same information as in the previous problem,  What is the recombination frequency between each gene pair? Round your answer to 2 decimal places.

recombination frequency between P/F =

recombination frequency between P/W =

recombination frequency between F/W =

3.) What is your coefficient of coincidence and your interference value for the previous data set? Use your rounded answers from the previous question. Round to 2 decimal places.

CC =

I =

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An individual is heterozygous for 3 genes (A/a B/b and C/c). He is crossed to an individual that is homozygous recessive for the same 3 genes (a/a b/b and c/c). The following offspring were seen. Which of the following phenotypes represent a double crossover event? (Hint - are you seeing all of the phenotypes in the next generation that you expected to see?) Select all that apply.

a) ++c

b) +bc

c) +++

d) abc

e) +b+

f) a++

g) ab+

h) a+c

Kernel Phenotype Number Yellow, Shrunken 349 Starchy, Shrunken 5 Yellow 3 Wildtype 99 Starchy 343 Shrunken 141 Starchy, Yellow, Shrunken 97 Starchy, Yellow 143 Total 1180

Explanation / Answer

Question 1

Parntal phenotypes : Yellow (P), Shrunken (F)      and      Starchy (W)

To determine gene locus order:
Most common phenotypes Yellow (p), Shrunken (f) and Starchy (w) are parental: no recombinants
Rarest phenotype Starchy (w), Shrunken (f) and Yellow (p) will be the double-recombinants:
On Comparision we can observe that (f) locus changes phase ("flips") with respect to (p) and (w),     therefore (f) is in the middle
Hence, the gene order = P-F-W

Recombination frequency between P / F = (141 + 143) + (5 + 3) / 1180 = 0.24 = 24% = 24 m.u = 24 cM

Recombination frequency between F / W = (99 + 97) + (5 + 3) / 1180 = 0.17 = 17% = 17 m.u = 17 cM

Recombination frequency between P / W = (99 + 97) + (141 + 143) + (2 x 5) + (2 x 8) / 1180

                                                                  = 0.42 = 42% = 42 m.u = 42 cM

Co-efficient of co-incidence = frequency of double cross over observed / frequency of double cross

                                                over expected

frequency of double cross over observed = 5 +3 / 1180 x 100 = 0.67%

frequency of double cross over expected = frequency between P / F x frequency between F / W

                                                            = 0.24 x 0.17 = 0.041 = 4.1%

Thus coefficient of coincidence = 0.67 / 4.1 = 0.16

The defi nition of interference = 1 - coefficient of coincidence

                                               = 1 – 0.163

                                               = 0.83

Question 2.

Answer : (c) & (d)

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