Molecular cloning and analysis of forked locus in Drosophila ananassae

Drosophila ananassae, in spite of its unique genetic characters including high mutability and high frequency of male recombination has been little studied at the molecular level. Since the species is very similar to D. melanogaster, it is natural to expect that the high spontaneous mutation rate and male recombination may be caused by inserted mobile DNA elements, as in D. melanogaster. The present study was designed to determine whether or not most spontaneous mutations of the forked locus of D. ananassae are caused by insertion sequences as is found in D. melanogaster. I cloned the forked locus of D. ananassae, using forked DNA from D. melanogaster as a probe and investigated the molecular structure and transcription of the gene by Southern and Northern analyses. The results suggest that the restriction map and transcriptional patterns of the forked locus of D. ananassae are similar to those of D. melanogaster, while the spontaneous mutations available in D. ananassae are induced quite differently from those that have been described in D. melanogaster; in four (f;cd, f10-14, f49 and f86) out of eight forked alleles, neither insertions nor deletions were detected around the forked coding region. Forked transcripts are expressed in a pattern which is very similar to that of D. melanogaster and were all of normal size in these mutants. The other four mutants (f10-3, f9-10, f83i and f79b) had insertion sequences upstream of the forked coding region, while transcripts of the forked gene were of normal size. Hence, none of the eight mutations studied appear to affect the structure of the forked transcripts.