Genomic nanos fragment in which the nanos 3'UTR has been replaced with the αTub84B 3'UTR. +1 element sequences (nucleotides 6-96) of the nanos 3' UTR and +2' element sequences (nucleotides 97-185) of the nanos 3' UTR have been inserted into the αTub84B 3' UTR sequences; they are separated by 130bp of αTub84B 3' UTR sequence.