BIOL 200 Lecture Notes - Lecture 16: Dna Replication, Semiconservative Replication, Thymine
7 Jun 2016
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Document Summary
Meselson and stahl experiment: test 2 basic models dna replication, 2 anti-parallel strands of dna at time = 0 (labelled, conservative mechanism. New dna molecule has 2 new strands: semi conservative mechanism. Separated strands each used as template for new strand. Labelling of dna: labelling molecular cohorts during synthesis, macromolecules synthesized during certain time period (the pulse) will incorporate labelled precursors, ways to label precursors, use precursors whose atoms are substituted by a detectable isotopic variant. Meselson stahl experiment used isotopes of varying density: use precursor chemical derivatives with detectable structural modifications. Chemical derivatives have weakened precursors, isotopic method has no chemical changes done to precursors. Meselson-stahl experiment (1958: stable n isotope 15n behaves chemically like normal n (14n) though the extra neutron makes 15n compounds denser than the corresponding 14n compounds, dna has characteristic buoyant density (~1. 7 g/cc) but 15n containing.
