In Drosophila melanogaster, cut wings (ct) is recessive to normal wings (ct+), s
ID: 56677 • Letter: I
Question
In Drosophila melanogaster, cut wings (ct) is recessive to normal wings (ct+), sable body (s) is recessive to gray body (s+), and vermilion eyes (v) is recessive to red eyes (v+). All three recessive mutations are X-linked. A female fly with cut wings, sable body, and vermilion eyes is crossed to a male with normal wings, gray body, and red eyes. The F1 females produced by this cross were mated with cut, sable, vermilion males in a testcross. The following are the progeny resulting from the testcross.
v ct s 510
v+ ct s 1
v+ ct+ s 14
v+ ct+ s+ 500
v+ ct s+ 73
v ct s+ 20
v ct+ s 81
v ct+ s+ 1
Total à 1200
What is the correct genetic map with respect to gene order and distances (in cM) for these three genes?
A)s 13 ct 3 v
B)s 3 v 13 ct
C)v 13 ct 3 s
D)s 26 v 3 ct
E)ct 13 s 3 v
Explanation / Answer
Option B is the answer .
v+ ct+ s 14
v ct s+ 20
the distance between the s -v gene is 14+20+1+1 /1200 *100 equal to 3.0 cM
v ct+ s 81
v+ ct s+ 73
The distance between the v-ct gene is 81+73+1+1/1200*100 equal to 13.8cM