Questions 22-24 refer to the following scenario. In Drosophila melanogaster , th

Question

Questions 22-24 refer to the following scenario. In Drosophila melanogaster, the recessive allele for the sepia locus causes flies to have very dark colored eyes. The recessive allele at the ebony locus causes the fly to have very dark body color.

A male from a true breeding line of sepia eyed-tan bodied flies (line A) is crossed to a female from a true breeding line of red eyed, ebony-bodied flies (the “wild type” line B) to create an F1:

Next, a female from the F1 is crossed to a male from line C, a sepia-eyed, ebony bodied, line of flies.

The phenotypes of 1000 progeny from this test cross were scored as follows:

Eyes    Body                  Number Observed

Red      Normal                             450

Sepia   Normal                               50

Red     Ebony                                 49

Sepia   Ebony                               451

22. What was the genotype of the F2 offspring which were RED NORMAL?

A) se se EB EB

B) se EB

C) se eb

D) SE se EB eb

E)Can’t tell because of linkage

23. Assuming that this is a fairly ordinary test cross, do a Chi-Square test of Observed vs. Expected values. Use independent assortment to generate your expected values. What is the value of c2?

A) 40

B) .016

C) 643

D) 16

E) 10.4

   P

                                                           .50 .05           .001

Degrees of freedom                 1         .45         3.84           6.63

                                                2       1.39        5.99            9.21

                                                3       2.37        7.81          11.34

24. Based on the table above (which is similar to the one in your lab manual, in the appendix), which of the following could reasonably be concluded from your Chi-square value from question 23?

A) Independent assortment is supported, the loci are linked.
B) Independent assortment is rejected because the Chi-square value is smaller than the critical value.
C) Independent assortment is supported because the Chi-square value is small.
D) The Chi-square value is larger than the critical value, thus, independent assortment is falsified.

E) The Chi-square value is too large to show anything

Explanation / Answer

1.Can’t tell because of linkage

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