BIOL 4374 Lecture Notes - Lecture 6: The Double Helix, Helicase, Isotopes Of Nitrogen
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2 Feb 2017
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Dna replication made possible by base pairing. Lecture 6- 2/2/2017: a-t, g-c, the new strand will be made so that it can pair up with the old strand, parent double helix (cid:498)donates(cid:499) each strand to make (cid:884) daughter helix"s. The daughter helix"s consist of one new strand and one old. Meselson and stahl dna replication was semiconservative. Grew bacteria in 14n or 15n: the n gets incorporated into the dna. Then they centrifuged to form cesium chloride density gradient: the 15n bacteria had bands at high density. The dna incorporated heavy n: the 14n bacteria had bands at low density- near the top of the tube. They then transferred bacteria grown in 15n to a 14n medium: after centrifugation the bacteria had bands of mid-density, meaning that the dna molecules had intermediate weight. Dispersive replication was ruled out by heating the dna to denature and carrying out more centrifugation: begins at replication orgins.
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