in the meselson and stahl model, which of the following would rule out a dispersive replication model? 1. in the first generation, you see a single band of intermediate density 2. in the third generation, the dna is composed of mixed dna molecules, some of them intermediate density, most of them light 3. in the second generation, you have 1 band of intermediate density 4. in the first generation, you see 2 bands, a light one and a heavy one 5. both 2 and 4