BIOL 101 Homework #3
1.) If Meselson and Stahl had only measured the density of the DNA for one generation after the “chase” phase of the experiment, their data would have ruled out only the conservative model of replication, leaving the semiconservative and dispersive models as equally viable. If DNA replication abided by the conservative model, each parental DNA molecule after time zero would have produced one daughter strand comprised of only parental N15 subunits, while the other daughter strand would have been comprised of subunits that incorporated only N14. According to this model, one would have expected to see two distinct bands appear in the UV absorption photographs, one representing N15 and the other N14. However, the data from…show more content… The paper is better for two reasons. First, although Meselson and Stahl conducted a very elegant and ingenious experiment, their paper lacked a concrete mechanism like Kornberg’s DNA polymerase. Kornberg’s work demonstrated that only one intact and continuous parental template strand is needed to encode a complementary strand via base pairing, giving rise to a new and cohesive double-stranded DNA molecule. The conservative model necessitated two parental subunits for replication and the dispersive model would have required smaller, fragmented subunits of the parental DNA. Because neither of these conditions were necessary for replication, the experiment conclusively supported the semiconservative model. Secondly, Kornberg’s experiment also distinguished decisively between the semiconservative and dispersive models. Meselson and Stahl required a second experiment to prove that each subunit of DNA was continuous, while this was inherent in the observed action of DNA polymerase. Because Kornberg’s work lacks as many variables, the paper has a lesser margin for error and comes to the same conclusion more