A heat shock promoter drives expression of a truncated Sb cDNA which lacks sequence coding for the protein sequence C-terminal to amino acid residue 257.
35% of flies expressing two copies of SbCD-TM-knot.hs (using four 1 hour heat shocks at 25, 27, 29 and 31 hours AP) in a Df(3R)sbd105/+ background have a blunt-ended bristle phenotype.