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BCH4024 - McKenna Lecture 48

BCH4024 - McKenna Lecture 48 - Central Dogma of Biology...

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1 “Central Dogma” of Biology I-DNA can replicate II-DNA can be transcribed into RNA III-mRNA can be translated into protein sequences Proteins determine (3D) our phenotype DNA RNA PROTEIN RNA Replicase DNA POL RNA POL Reverse Transcriptase Semi-conservative Ordered and sequential Uses activated substrates Very Accurate Numerous enzymes Template Driven A. DNA: DOUBLE TEMPLATE MOLECULE 1. Strands separate, each becoming template for assembly of a complementary strand RESULT: TWO IDENTICAL MOLECULES FROM ONE: 2. Replication is “semi-conservative Meselson-Stahl experiment confirmed basic hypothesis. Parental strands are conserved during subsequent rounds of replication. DNA REPLICATION Parental Duplex Intermediate in semiconservative replication Two daughter Duplexes Each strand is a template for a new Strand P P P P P P N N N N -Use of density gradients
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2 The Meselson-Stahl Experiment 3. Base pairing rules completely dictate the sequence of the newly synthesized strand ( Watson-Crick ) Some Features of Replication Leading Lagging strand strand “okazaki fragments” continuous discontinuous synthesis synthesis Single stranded DNA template 5’ 3’ DNA RNA RNA primer Attached by primase (part of primosome) Newly synthesized strand. RNA primer is removed and gap is filled by DNA pol 1 DNA ligase joins bases DNA REPLICATION DNA Pol 1 DNA POL III RNA Polymerase Primer DNA Ligase
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