43DNAReplicationandRepair

43DNAReplicationandRepair - 4.3. DNA Replication and Repair...

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4.3. DNA Replication and Repair (pp. 217-222) Synthesis Phase  (of cell cycle):  “DNA replication”   - ensure that daughter cells have same number + kind of DNA as the parent cell after      mitosis   DNA Replicates Semi-conservatively   Meselson and Stahl  (1958) :   “DNA replicates semi-conservatively” (Fig. 1, p. 217).      orig. strand of DNA   Semi-conservative       new strands of DNA         replication        orig. strand of DNA        1.  E. coli (its orig. DNA contain  14 N) put in nutrient medium containing radioisotope  15    (i.e. “heavy” nitrogen)   after 17 generations, all bacterial DNA had  15 N   - DNA extracted, centrifugated   DNA seen as heavy “density band” (Fig 2, p. 218). 2. E. coli (with  15 N) put in nutrient medium containing regular  14 N (i.e.  14 NH 4 )   - after one generation, DNA extracted, centrifugated    DNA seen as intermediate “density band”  evidence that DNA of both  14 N-stands and  15 N-strands are intertwined in         same double-helix   With subsequent generations:    -    more     of the “light” DNA is seen
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This note was uploaded on 12/06/2009 for the course BIO BLG143 taught by Professor Kimberleygilbride during the Fall '09 term at Ryerson.

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43DNAReplicationandRepair - 4.3. DNA Replication and Repair...

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