Restriction Enzyme Polymorphisms in the Region of the Small Heat Shock Genes in Drosophila

Abstract

A survey of restriction enzyme polymorphisms was performed with fifteen iso-female lines of D. melanogaster amd eighteen single representaives of other Drosophila species. Three enzymes: Bam H1, Eco R1, and Pst 1 were used to probe the genetic structure of the region containing the genes Hsp 22, Hsp 23, Hsp 26, and Hsp 27. The results for within D. melanogaster show that all variation in the DNA sequence is limited to the non-coding region. The restriction patterns confirm the hypothesis that the hsp 22-27 genes are a result of tandem duplications. The values for Nei's estimate of sequence diversity (delta) are 0.034 between populations of D. melanogaster, 0.113 between sibling species, and 0.123 between nonsibling species. These estimates were compared to values obtained for protein and enzyme variation. DNA sequence divergence between nonsibling species versus nonsibling species show less differentiation than protein and enzyme divergence. The restriction enzyme phenotype was used to generate phylogenies which is in approximate agreement with previously reported phylogenies. Molecular drive and selectionist hypotheses of differential rates of evolution during cladogenesis and anagenesis are discussed.