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Cell Biology Homework

1. When DNA samples A and B were separated by buoyant density centrifugation the two samples migrated 23 and 15 cm, respectively. If DNA B had a GC content of 34%, what was the GC content of DNA A?

2. If Meselson and Stahl found that the ratio of 15N-labeled single-strands to 14N-labeled single-strands was 2:6 in the second generation, what would be the ratios for the fourth and fifth generations?

3. In the first generation of growth on 15N containing media, a single band of DNA having an intermediate density was detected by buoyant density centrifugation using a neutral CsCl gradient. If the dispersive model of replication was true, what result would have been seen? What would be the result in the second generation? How would that compare to the semi-conservative model?