UASt regulatory sequences drive expression of a bab1 minigene, which consists of a 2.7kb PstI-SalI genomic fragment (starting 6bp upstream of the ATG codon and ending 422bp after the 5' splice site of intron 1) and a 4.5kb BamHI genomic fragment (starting 146bp upstream of the 3' splice site of exon 1 and ending 273bp after the end of the bab1 cDNA).