An interchromosomal gene conversion of the Drosophila dunce locus identified with restriction site polymorphisms: a potential involvement of transposable elements in gene conversion.

Females heterozygous for the two alleles dnc2 and dncM14 of the X-linked gene dunce (dnc), and carrying a copy of dnc+ on the second chromosome, have produced a cluster of six dnc+ progeny X-chromosomes from recombination experiments. Restriction site polymorphisms have been used as genetic markers to follow the parentage of dnc locus segments in these chromosomes. All six chromosomes are identical with respect to the spectrum of restriction site markers they carry in the dnc+ chromosomal region. In the progeny chromosomes, this region is comprised of sequences like the dncM14 X-chromosome and the translocation copy of dnc+. Sequences flanking the dnc gene in the progeny chromosomes are like the dncM14 chromosome. Internal to the gene but near the 5' end, is a segment from the dnc+ translocation which has apparently originated from an interchromosomal and premeiotic gene conversion event. In addition, two transposable elements have inserted into the progeny chromosomes, one towards the 5' end of dnc and the other near the 3' end. The insertion of these elements occurred premeiotically since all six chromosomes are structurally identical. The data are interpreted with respect to a potential role of transposable element transposition in the process of gene conversion.