Genetics professors!! people that love genetics!! genetic nerds! this one is for YOU!?

Question

In drosophila white (w), is s*x-lined recessive mutation blocks pigment in eye. Scarlet,st, is an autosomal recessive mutation that blocks formation of brown eye pigment, thereby brightening the eyes from the normal red to a more crimson color. predict the F1 and F2 phenotypes of the following matings, assuming the parents are true-breeding, single mutants:

A) white male x scarlet female

B) scarlet male x white female

Answer 1

A.

F1, all offspring will be scarlet

F2, all females will be scarlet, 50% males will be white-eyed and the other 50% will be scarlet.

B.

F1, all females will be scarlet, all males will be white-eyed

F2, 50% females will be white-eyed, 50% females will be scarlet; 50% of the males will be white-eyed, 50% will be scarlet.

White is dominate over scarlet (and also another gene called brown)(brown eyes).

Wild type eyes are dominate over white and scarlet.

Scarlet is NOT on the X chromosome (that's what being autosomal means).

In the first cross, all the F1 females have one X carrying a wild type white and another X carrying white. (Ww)  They also have one wild type autosomal chromosome for Scarlet and one autosomal chromosome carrying scarlet (Ss).  Since there is one wild type allele at each of these loci, the females will have wild type eyes.