lecture07

lecture07 - 20.106J Systems Microbiology Lecture 7 Prof....

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20.106J – Systems Microbiology Lecture 7 Prof. DeLong ¾ Problem set 2 due today. ¾ For next week: we’ll be doing Chapter 8 of Brock ¾ Exam in a week and a half ± Slide: Central Dogma o Replication, Transcription, Translation o Reverse transcription sometimes ± Slide: Flow of information o Right now we’re just thinking about information flow within an individual species – how nucleic acid information flow occurs o How you maintain fidelity and copy your DNA for all your daughter cells ± What we know about DNA: o The four bases o The ring system of the sugar ± The number of carbons ± How you tell the difference between DNA and RNA (the lack of oxygen) o The nomenclature of the bases o Alternating linkage (3’ and 5’) o The base pairing (G-C, A-T) –This is how it replicates with such high fidelity. o Anti-parallel (5’ Æ 3’, 3’ Æ 5’) o When the structure was first determined, the pairing was inferred, but the method of replication wasn’t clear ± It could have been Semiconservative, Conservative, or Random Dispersive. ± These different methods incorporate the mother strands into the daughter strands in different ways. ± To determine this, they added 15 N labels experimentally – they could predict the densities resulting from each replication method – heavy vs. light ± The Conclusion, of course, was that it was semiconservative. o The replication process is not simple, and involves a lot of enzymes. ± Polymerase III can’t just set down on a DNA strand – it needs a DNA primer. That primer is then used to extend the DNA strand. ± This means that initially it’s not just a DNA strand – it’s a DNA-
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lecture07 - 20.106J Systems Microbiology Lecture 7 Prof....

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