pe N. Th Generations 0 0.3 0.7 1.0 1.1 us1.5 1.9 M DNA bands Density gradient Figure B The evidence for semi-conservative replication. The DNA is isolated and separated by centrifugation at different times, with the results shown. At time 0, a single band is observed at the high 15N density. By the end of the first generation, a single band is seen at a slightly lower density, demonstrating that the DNA has one strand labeled with 14N and one strand labeled with 1N. Source: Meselson and Stahl (1958) PNAS, 44, 671.
This is a three part question:
Figure B in Box 4.1 illustrates the results of the Meselson-Stahl experiment after a single cycle of replication in 14N.
(a) Explain the results they observed after two rounds of replication in 14N medium.
(b) Draw out the expected results if a third round of replication were allowed in 14N medium.
(c) Two other models for template-directed replication were considered as alternatives to semi-conservative replication. One of these was conservative replication, in which the parental strands were unpaired, replicated, then reannealed such that the parental strands stayed together and the newly synthesized strands were together. The second model was dispersive replication, in which one strand was used as the template for
Trending now
This is a popular solution!
Step by step
Solved in 3 steps with 1 images
