DNA Replication - DNA replication & repair. Chapter 20...

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Chapter 20 (1st edition chapters 17-18)
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Central dogma of molecular biology:
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Review DNA structure. Negative charge on phosphoryl groups.
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Review DNA structure. Watson-Crick base pairing: Hydrogen bonding lets A recognize T, G recognizes C. 5’ 5’ 3’ 3’
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When DNA structure was discovered in 1953, it was immediately recognized that DNA could serve as a template for its own replication.
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“It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material.”
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DNA replication: Circular bacterial DNA caught in the act.
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The helices of DNA are “negatively supercoiled”.
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DNA topoisomerase is an enzyme that can change the amount of supercoiling in DNA: To change supercoiling, topoisomerase breaks and re-joins the DNA strands . The process requires energy (provided by ATP hydrolysis).
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Type I Topoisomerase breaks one DNA strand, then re- connects the DNA. ( Type II topoisomerases break both DNA strands before re-sealing the DNA)
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Type I topoisomerases temporarily attach the broken DNA strand to a tyrosine, before re-joining the DNA strands again.
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All living things (eukaryotes, bacteria & archaea) use topoisomerases during their DNA replication process. Several antibiotics interfere with bacterial topoisomerases (example: ciprofloxacin). ciprofloxacin Ciprofloxacin is a "fluoroquinolone", and is in the top 20 most prescribed drugs. It inhibits a bacterial type II topoisomerase. Topoisomerase is also known as “DNA gyrase” .
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topoisomerases? The eukaryotic and bacterial topoisomerases are similar, but sufficiently different so that the antibiotic only kills the bacteria. In general, what are the properties of a good antibiotic?
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This note was uploaded on 06/20/2011 for the course CHEM 369 taught by Professor Hoffman during the Spring '11 term at University of Texas at Austin.

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DNA Replication - DNA replication & repair. Chapter 20...

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