A portion of the per 3'UTR present in per+t13.2 has been replaced with a KpnI-Bsu36I fragment containing the corresponding per 3'UTR sequence from Australian flies carrying the SNP3G haplotype. The exchanged fragment extends from the stop codon to approximately 70bp upstream of the site for 3' cleavage/polyadenylation. Three copies of the Tag:FLAG epitope have been inserted just upstream of the translation stop codon.