One interesting aspect of this research are the ramifications concerning the regulation of sexual orientation. Whereas wild-type males normally recognize only females as appropriate courtship objects, fruitless mutants court males and females indiscriminately. The illusion of the dual nature of sexual characters is belied by the complexity of their regulation. The fruitless transcription unit produces at least seven overlapping classes of transcription. The presence of three different 5' ends suggests that there are at least three promoters.
Most transcripts contain a common middle region.
There are at least four alternative 3' ends. It is not known whether transcripts with a particular 5' end can have all the possible 3' ends and vice versa. Similar 13 nucleotide repeats are repeate six times in Doublesex . The FRU BTB domain is followed by stretches of repeated amino acids. The carboxy-terminus of the proteins contains a zinc finger pair related to the C2H2 class.