Genomic nanos fragment in which the nanos 3'UTR has been replaced with the αTub84B 3'UTR. +2' sequences (nucleotides 97 to 185 of the nanos 3' UTR) followed by +1 element sequences (nucleotides 6-96 of the nanos 3' UTR) are inserted within the αTub84B 3' UTR sequences. A Tag:HA epitope has been inserted at the 5' end of the nanos coding region.