A cDNA fragment containing mutated H sequence has been reintroduced into the attP site present in HattP, resulting in a H locus lacking introns and carrying a mutation in the first possible start codon (amino acid replacement M1V). A residual attR site is present in the 5'UTR and a loxP cassette containing a w[+] marker is present in the 3'UTR.
Adult HΔM1.w+ homozygous mutants display rather mild bristle defects with, on average, 6 (out of 40 present in wild-type) of the large head and thorax bristles affected. Wing venation remains largely normal.