$db_query = "SELECT ST.sno_name,HT.homolog_name FROM sno_Table ST, Homolog_Table HT,sno_Homologs SH,Organism O WHERE ST.sno_id=SH.sno_id AND SH.homolog_id=HT.homolog_id AND HT.org_i d=O.org_id and (ST.family=?) and O.organism=?";

...

$sth->execute($family, $TB);