MBB 222 Lecture Notes - Lecture 17: Klenow Fragment, Dnaa, Dna Supercoil
4 Mar 2016
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Document Summary
Cells require topoisomerases to perform vital functions, such as dna replication, packaging or gene expression. Quinolones inhibit bacterial dna gyrase, a type ii topoisomerase by blocking the last step of the topoisomerase reaction, the resealing of the dna strand breaks. Ciprofloxacin (cipro) is one of the few antibiotics reliably effective in treating anthrax infections, and is considered a valuable agent in protection against possible bioterrorism. Conservative: one daughter molecule is completely new dna while the parental stand remains intact. Semiconservative: each daughter molecule possesses one parental strand. Meselson-stahl experiment (1957): (a) e. coli was grown for many generations in 15nh4cl. The 15n heavy isotope became incorporated into the bacterial dna, which sediments as a single band using cscl density gradient centrifugation (blue). (b) the cells were then transferred to a medium containing 14nh4cl. Replication fork: dynamic point where parent dna is being unwound and a new strand is being synthesized.
