midterm II notes

midterm II notes - DNA Packaging Histones Level 1-...

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DNA Packaging Histones Level 1- nucleosome Level 2 – solenoid Level 3- scaffold Level 4 – scaffold wound up Theories of how replication works Semiconservative o Correct… mother and daughter strand Conservative o The original DNA stays, and completely new daughter strands make a new DNA Dispersive o Segements of the DNA are old, new, old, new, etc. Messelson and Stahl’s work Grew DNA in 15 N Added 14 N nucleotides Observed that new DNA was semiconservative Replication Initiation o OriC – origin of replication/start site o AT rich (double bonds easier to cleave) Unwind o Helicase- unwinds/ unzips o SSB protein- single strand binding protein protect ss DNA from renaturing or destroyed o Toipoisomerase- prevents over twisting, relaxes the strain Add nucleotides/extend o DNA Polymerase III polymerization 5’ to 3’ exonuclease fxn at end, (cuts nucleic acid) 3’ to 5’ (it backs up to proofreed) o RNA Primer Must be laid down to begin polymerization o Primase Lays down the RNA primer o Okazaki Fragments Fragments on the lagging strand Clean up/connect o DNA Polymerase I Exonuclease (cuts nucleic acid) 5’ to 3’ removes RNA primer
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o Ligase Pastes up pieces were RNA primer was removed Types of RNA rRNA- ribosomal mRNA- messenger tRNA- transfer siRNA- silencing snRNA- small nuclear
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midterm II notes - DNA Packaging Histones Level 1-...

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