In the fruit fly, drosophila melanogaster, a known deletion on the x chromosome removes both a gene involved in the fly's development and the gene for eye color. the deletion is lethal when homozygous or hemizygous. flies that are heterozygous for the mutation are viable, but have indentations at the wing margin. therefore, the deletion is named the notch mutation. the allele for wild type eyes is dominant over the allele for white eyes.