Restriction enzyme analysis of a highly diverged satellite DNA from Drosophila nasutoides

The satellite II DNA of Drosophila nasutoides is a highly diverged repetitive DNA, showing about 17% base changes between repeat units (Cordeiro-Stone and Lee, 1976). This DNA is cleaved by four different restriction enzymes to produce multimeric fragmentation patterns, indicating that their restriction sites are regularly arranged. Moreover, all four enzymes produce identical fragment lengths, the size of a monomer being 96 base pairs. Such multimeric patterns are expected for a diverged repetitive DNA, since many restriction sequences could have undergone changes during sequence divergence. Further restriction analyses of this DNA by double digestions and cloning reveal that there are three different sequences in satellite II DNA with respect to the presence and the arrangement of various restriction sites (Fig. 7). As an example, one sequence contains many EcoRI sites and fewer HinfI sites (20% of EcoRI sites), which are arranged regularly. These observations suggest that satellite II DNA of D. nasutoides might have evolved through different modes of sequence divergence.