Hidden electrophoretic variation at the xanthine dehydrogenase locus in a natural population of Drosophila melanogaster.

Sixty-two isochromosomal lines of D. melanogaster were screened for cryptic electrophoretic variation at the xanthine dehydrogenase (XDH) locus. Sequential polyacrylamide vertical slab gel electrophoresis was performed using four electrophoretic criteria. A total of 15 classes of electromorphs were revealed. D. melanogaster appears to exhibit as much polymorphism at this locus as other extensively studied Drosophila species.--No evidence for loci on the X or second chromosomes which modified XDH mobility was found. Six of the electromorphs were mapped to the Xdh (ry) structural locus. Eight of the remaining nine classes exhibited mobility variation consistent with structural variation at the Xdh locus. The final class exhibited aberrant patterns and is under further study.