Figure 2.

(Upper) Southern blot showing that HeT-A^mel DNA cross-hybridization decreases sharply with evolutionary distance. ³²P-labeled sequence from the 3′ noncoding region shows strong hybrdization to DNA from D. melanogaster (Oregon R stock), D. mauritiana, and D. simulans (separation 2–3 My). No hybridization is detected with more distantly related species. Sequence from the coding region (ORF) shows almost the same hybridization as the noncoding region but also reveals faint bands of hybridization to D. yakuba and D. teissieri (separation from D. melanogaster, 5–16 My). DNA was cut with EcoRI. The final wash of blot was 2× SSC at 65°C. Size markers (in kb) are from a DNA ladder. (Lower) Diagram of the evolutionary relationships of species used in this work (largely from ref. 13).