Class of Gene	Effect of Mutations	Examples of Genes
Gap genes	Delete adjacent segments	hunchback, Krüppel, knirps, giant, tailless
Pair-rule genes	Delete same part of pattern in every other segment	runt, hairy, fushi tarazu, even-skipped, odd-paired, sloppy paired, odd-skipped
Segment-polarity genes	Affect polarity of segment; part of segment replaced by mirror image of part of another segment	engrailed, wingless, gooseberry, cubitus interruptus, patched, hedgehog, disheveled, costal-2, fused