In Drosophila melanogaster, two independently assorting loci thataffect wing sha
ID: 4970 • Letter: I
Question
In Drosophila melanogaster, two independently assorting loci thataffect wing shape are known. Flies homozygous for therecessive be mutant allele at one locus (and otherwise wild type)have bent wings. Flies homozygous for the recessive ap mutantallele have no wings at all, regardless of their genotype at otherloci. All other genotypes give normal wings. If a truebreeding bent winged fly is crossed with a fly with no wings thatis homozygous for the normal be+ allele and the apallele, what proportion of the F2 should have no wings?The F2s are produced by crossing F1 XF1. (Hint, be sure to draw out the cross.) Do you seeepistasis here?Explanation / Answer
a true breeding bent winged fly x a fly with no wings that is homozygous for the
normal be+ allele and the ap allele
be be ap+ ap + be+be+ ap ap
be ap+ be+ap-----------------gametes
be+be ap+ ap winged---------------F1
be+ be ap+ ap x be+ be ap+ ap
gametes
be+ ap+
be+ ap
be ap+
be ap
gametes
be+ ap+
be+ ap
be ap+
be ap
be+ ap+
be+ ap+
be+ ap+
be+ ap+
be+ ap
be+ ap+
be ap+
be+ ap+
be ap
be+ ap
be+ ap+
be+ ap
be+ ap
be+ ap
be+ ap
be ap+
be+ ap
be ap
be ap+
be+ ap+
be ap+
be+ ap
be
gametes
be+ ap+
be+ ap
be ap+
be ap
be+ ap+
be+ ap+
be+ ap+
be+ ap+
be+ ap
be+ ap+
be ap+
be+ ap+
be ap
be+ ap
be+ ap+
be+ ap
be+ ap
be+ ap
be+ ap
be ap+
be+ ap
be ap
be ap+
be+ ap+
be ap+
be+ ap
be