Structural heterogeneity of mitochondrial DNA molecules within the genus Drosophila.

Abstract

The MW of circular mitochondrial DNA (mtDNA) molecules from 39 species representing 13 groups of 5 subgenera of the genus Drosophila were determined by EM. mtDNA molecules of all species examined, other than members of the melanogaster group, had, with 1 exception, MW in the rather narrow range 9.90 .cntdot. 106 to 10.34 .cntdot. 106. The 1 exception was D. robusta, which had a MW of 10.61 .cntdot. 106. In contrast, mtDNA molecules from species within the melanogaster group had MW covering the considerably greater range 9.92 .times. 106 to 12.35 .cntdot. 106. Applying the EM denaturation mapping technique of Inman to mtDNA molecules of 8 species of the melanogaster group, each of them contained a region [presumably rich in adenine and thymine (A+T)] which denatured at a specific temperature (40.degree.) at which most of the remainder of the molecule remained undenatured. The size of the A+T-rich region was constant for mtDNA molecules of different species. The differences in MW of the A+T-rich regions can almost completely account for the differences in total MW of the mtDNA molecules from species of the melanogaster group.