Mutated His3 gene (amino acid replacement K27R, to prevent methylation) in the context of a histone gene repeat unit.
Flies expressing M{3xHisGU.H3K27R} in a Df(2L)HisC mutant background die toward the end of embryogenesis.
Df(2L)HisC 4xM{3xHisGU.H3K27R} mutant clones show homeotic transformation into more posterior body segments; the mutant sensory bristles are finer and more tapered than the neighbouring wild type bristles in A2 and resemble bristles characteristic of abdominal segment A10 in wild type animals.
Wing disc clones containing Df(2L)HisC mutant cells stop proliferating, but this phenotype is rescued in animals that also carry four copies of M{3xHisGU.H3K27R}.