Question 1 In Drosophila the Xlinked recessive mutation verm

Question 1 In Drosophila, the X-linked recessive mutation vermilion (X causes bright red eyes, in contrast to the brick-red eyes of wild type (X A separate autosomal recessive mutation (bn, causes the eyes to be brown. Flies carrying both mutations lose all pigmentation and are white- eyed Part A Predict the F1 results of the following cross: white females x normal males. (Assume that the parents are homozygous.) Label the diagram by dragging the labels to the appropriate targets. Note: Not all labels will be used. female, normal female, brown eyes female, vermilion eyes female, white eyes male, normal male, brown eyes male, vermilion eyes male, white eyes Submi My Answers Give Up Part B This question will be shown after you complete previous question (s). previous l 1 of 6 l next Provide Feedback Continue

Solution

Ans:

Where you have one X-linked and one autosomal it is easier to treat the two genes separately and combine the results at the end

(a) For vermillion, v the female is XvXv and the male X+Y. The female produces all Xv gametes and the males either X+ or Y. F1 females will be all X+Xv and the males will all be XvY.

For brown, b females are ++ and males bb. F1 of both sexes will be +b.

Now combine. Females are all +b X+Xv and have one wild type allele (+) for both genes, so will have normal wild type red eyes.

Males are all +b XvY and are normal at the brown locus, but are all vermillion, so will have vermillion eyes.

Your F1 cross:

Vermillion X+Xv x XvY. Females produce 1/2 X+ and 1/2 Xv gametes, males 1/2 Xv and 1/2 Y.

Female F2 are X+Xv and XvXv. Males are X+Y and XvY.

Brown +b x +b. Both produce + and b gametes which combine to produce ++ +b b+ and bb, the first

Now combine. F2 females will be 1/2 X+Xv x 1/4 ++ = 1/8 X+Xv++ normal wild type eyes
and 1/2 X+Xv x 1/2 +b = 1/4 X+Xv+b normal wild type eyes. Finally 1/2 X+Xv x 1/4 bb = 1/8 brown eyes.

Then 1/2 XvXv x 1/4 ++ = 1/8 XvXv ++ vermillion eyes; 1/2 XvXv x 1/2 +b = 1/4 XvXv +b vermillion eyes and 1/2 XvXv x 1/4 bb = 1/8 V=XvXvbb white eyes.

F2 males 1/2 X+Y x 3/4 ++ or +b = 3/8 X+Y++/X+Yb+ brown eyes, 1/2 X+Y x 1/4 bb = 1/8 X+Ybb brown eyes.

1/2 XvY x 3/4 ++/+b = 3/8 XvY++ or +b vermillion eyes and 1/2XvY x 1/4 bb = 1/8 XvYbb white eyes.

You will have to tidy up these results and then repeat the same methods. The results will be the same for brown in b). The vermillion cross is X+X+ x XvY.

For c the crosses are XvXvbb x X+Y++, which you can split into two crosses and repeat using the same method.

2. a) The cross is XvXvbb++ x X+Y++ss. Use what results you can from earlier crosses and then combine with sepia.

b) the cross is X+X+++ss x XvYbb++