upd1 unpaired 1 Unpaired/Out-stretched Os unp outstretched-smalleye Outstretched Upd1 odsy unpaired UPD Upd Unpaired od l(1)YM55 Unpaired 1 upd homolog CG5993 Unpaireds outstretched small eye sisC sis-C l(1)YC43 outstretched os OS sy upa unpaired1 small-eye UPD1 upd sisterless c sis-c gene