A bilateral gynandromorph of D. melanogaster (heterozygous for 2 loci) is formed after one of its two X chromosomes is lost in one of the two cells during the first mitotic division.

The left side is composed of male cells containing a single X and expresses the mutant white-eye and miniature-wing alleles.

The right side is composed of female cells containing two X chromosomes heterozygous for both alleles.