Unformatted text preview: s semi-conservative
Expected results second generation shift
HL LH LH LL LL H L
LL H L 9 Does DNA replication begin at the same site in every replication cycle? 10 E. coli chromosome replication
theta, θ, structure After round 1 Fig 20. 9 Round 2
11 Does DNA replication begin at the same site in every replication cycle?
Experiment: 1. Pulse-label a synchronized cell population during successive rounds of DNA replication with two different isotopes, one that changes the density of newly synthesized DNA (15N), and one that makes it radioactive (32P). 2. DNA is then isolated, sheared, and separated by CsCl density gradient ultracentrifugation. 3. Radioactivity (32P) in the DNAs of different densities is counted.
12 13 Prior to 1st replication cycle, 15N added briefly (“pulse”) Prior to 2nd replication cycle, cells were pulsed with 32P
15N 1st - heavy isotope of Nitrogen 32P - radioactive isotope of Phosphorus
14 15 16 17 DNA is isolated, sheared into fragments, and separated by CsCldensity gradient centrifugation. 18 19 Same Origin Random Origi...
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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.
- Spring '09