E(var) and Su(var) mutations

Mutations in genes whose protein products participate in chromatin modificationare detected by enhancement or suppression of position effect variegationMutations in genes whose protein products participate in chromatin modificationare detected by enhancement or suppression of position effect variegation

Variegated eye Su(var) mutations E(var) mutations Red patches are produced by cells in which W is transcribed, and white patches by cells in which W+ is inactivated by heterochromatin spread. Mutations block efficient formation of heterochromatin and leave most cells with active W+ transcription. Mutations enhance heterochromatin formation and re- strict W expression to small patches.