Introduction to Genetic Analysis 240

Introduction to - 7.3 Semiconservative Re0 GRIFFITHS FREEM Sample First Pages INR p 13 Application File on File hand side of Figure 7-13a precisely

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Unformatted text preview: 7.3 Semiconservative Replication 13 44200 GRIFFITHS FREEM Sample First Pages INR 12-10-2003 p 13 Application File on File hand side of Figure 7-13a), precisely as predicted by the Watson–Crick model. The replication fork Another prediction of the Watson–Crick model of DNA replication is that a replication zipper, or fork, will be found in the DNA molecule during replication. This fork is the location at which the double helix is unwound to produce the two single strands that serve as templates for copying. In 1963, John Cairns tested this prediction by allowing replicating DNA in bacterial cells to incorporate tritiated thymidine ([ 3 H]thymidine)— the thymine nucleotide labeled with a radioactive hydrogen isotope called tritium. Theoretically, each newly synthesized daughter molecule should then con- tain one radioactive (“hot”) strand (with 3 H) and another nonradioactive (“cold”) strand (with 2 H). After varying intervals and varying numbers of replication cycles in a “hot” medium, Cairns carefully lysed the bac- teria and allowed the cell contents to settle onto a piece...
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This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.

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