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 17
v⁺ ct⁺ s 4
v⁺ ct⁺ s⁺ 500
v⁺ ct s⁺ 56
v ct s⁺ 5
v ct⁺ s 61
v ct⁺ s⁺ 19
Total → 1172

What is the correct genetic map with respect to gene order and distances (in cM) for these three genes?

	ct 8.7 s 6.2 v
	s 4.5 v 15.6 ct
	s 12.5 ct 2.6 v
	v 3.8 s 10.8 ct