 In normal unmutated "Drosophila," each segment produces bristles called denticles in a band arranged on the side of the segment closer to the head (the anterior).They found five genes – "even-skipped, hairy, odd-skipped, paired" and "runt" – where mutations caused the deletion of a particular region of every alternate segment.For example, in "even-skipped," the denticle bands of alternate segments are missing, which results in an embryo having half the number of denticle bands.