Extent of genetic variation at a highly polymorphic esterase locus in Drosophila pseudoobscura

The esterase-5 locus of Drosophila pseudoobscura has been screened for variation by using a wide variety of electrophoretic conditions and by testing heat sensitivity. Among 50 isogenic lines from 17 populations, 21 genetic variants were found at the locus, 18 by electrophoresis and 3 by heat denaturation. Including alleles previously known, there are a total of 30 alleles at this locus in natural populations. This represents a doubling of the previous estimates of polymorphism at this locus. The study confirms that, in contrast to monomorphic loci, loci judged polymorphic under one detection procedure show large increases in polymorphism when examined extensively.