The loxP cassette in HΔM3.w+ has been excised. The locus encodes H lacking introns and carrying a mutation in the third possible start codon (amino acid replacement M148V). As a consequence only the p120 protein isoform cannot be produced. A residual attR site is present in the 5'UTR and a single loxP site is present in the 3'UTR.
Adult HΔM3 homozygous mutants do not display significant bristle defects with the number of aberrant bristles within the range observed in wild-type, no abnormalities in wing venation are seen either, but the wing size is significantly reduced compared to controls. However, when combined with the HattP allele, the transheterozygotes show very severe bristle defects (more than 30 affected).
H[+]/HΔM3 is a suppressor of visible | adult stage phenotype of DeltaB2
The wing notching phenotype of Df(1)N-54l9/+ heterozygotes is not significantly altered if they are also heterozygous for HΔM3.
The vein thickening and vein deltas characteristic for HattP/+ adults is partially suppressible by combination with a single copy of HΔM3.