So, I'm doing some drosophila experiments with my high schoolers and I had really poor production of wild type individuals for doing the experiment resulting in not enough to cross with everyone... I am trying the following crosses and hoping the kids can still learn from it, but wanted input from any fly-herders on what I can expect with the first two crosses....

Sepia males x White Eye females

Sepia females x White Eye males

Dumpy males x Wild-type females

Dumpy females x Wild-type males

I don't think the gender separation will make any difference except in the white x sepia crosses since it is X-linked. What should I get in the sepia x white crosses? Since they both control eye color and are both recessive I'm not sure. Am I correct that w is epistatic, thus should block sepia in an x-linked manner (same as if I had used wild-type instead of sepia)? I assume the Dumpy x Wild-type will go by the books (F1 all wild-type with F2 3:1 ratio). Fingers crossed.


1 Answer 1


I posted this on Reddit as well, so credit to km1116 for working this out. Here is his response which follows my original logic (though I'm not sure if he is right):

female x male:

w x se

F1: wild-type females and white males

F2: 1/4 white-eyed males, 3/16 wild-type males, 1/16 sepia males, 1/4 white-eyed females, 3/16 wild-type females, 1/16 sepia females

se x w

F1: all wild-type offspring

F2: 1/4 white-eyed males, 3/16 wild-type males, 1/16 sepia males; 3/8 wild-type females, 1/8 sepia females

wt x dp (either direction)

F1: all wild-type

F2: 3/4 wild-type, 1/4 dumpy

My rationale for his answer is the genotype of the cross looks like this:

XwYNN with XWXW nn , where "W" is normal eyes, "w" is white", N is Wildtype and n is sepia.


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