The Satellite DNAs of Drosophila virilis

When the DNA from diploid cells of Drosophila virilis is centrifuged to equilibrium in a neutral CsCl gradient, four major peaks are distinguishable (Fig. 1). These correspond to the main peak sequences (ρ = 1.700) and three large satellites numbered respectively I (ρ = 1.692), II (ρ = 1.688), and III (ρ = 1.671). Together the satellites constitute almost half the total DNA. Each of the satellites separates into strands of different buoyant density when the DNA is centrifuged to equilibrium in alkaline CsCl (Fig. 2). Satellite III can be isolated in an essentially pure form by recentrifuging the lightest fractions from a neutral gradient, and its separated strands can then be obtained from an alkaline gradient. Satellites I and II can be separated from each other on a Ag+-Cs2S04 gradient (Gall and Atherton, unpub.) or on a Hg+-Cs2S04 gradient (Blumenfeld et al., 1973). Their heavy and light strands can...