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Labeled, sheared DNA
20 Labeled DNA Result: ~50% (the most possible) of the incorporated 32P was in the same DNA that was shifted by 15N Conclusion: Replication of bacterial chromosome starts at the same place every time 21 Is replication unidirection or bidirectional? 22 Experiment: Drosophila cells (eukaryotic) 1. Labeled with pulse of highly radioactive precursor 2. Followed by pulse of lower radioactive precursor 3. Replication bubbles were viewed by EM and autoradiography. If Bidirectional: If Unidirectional: “mustache” Fig. 20.11
vs pair Conclusion: eukaryotic (and most prokaryotic) origins replicate bi-directionally!
24 Replicon = DNA replicated from a single origin Eukaryotes have many replication origins.
General features of DNA replication: DNA is replicated semi-conservatively The origin of replication is non-random Replication is bi-directional 26 Basic mechanics of replication
DNA polymerases synthesize DNA Replication produces leading and lagging strands DNA ligases join DNA strands together 27 DNA-dependent DNA polymerase
synthesize DNA from dNTPs requires a template synthesize from 5’ to 3’ (add nt to 3’ end only) 28 3’ 5’ 5’ 3’ 29 Problem 1: How does DNA pol begin a new strand ‘from scratch?’ Answer: It doesn’t!
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This note was uploaded on 04/10/2010 for the course BIO 51130 taught by Professor Moon during the Spring '09 term at University of Texas at Austin.
- Spring '09