DNA Replication and Repair

DNA Replication and Repair - DNA Replication and Repair(241...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
DNA Replication and Repair (241 – 253) DNA replication requires: Substrates (dNTPs) DNA polymerase DNA template 3 proposed mechanisms of replication: Semi-conservative (1 old strand, 1 new strand on each of 2 helices) Conservative (1 old helix, 1 new helix) Dispersive (2 helices with random old/new fragments) Meselsohn and Stahl experiment Hypothesis: Each DNA strand replicates semiconservatively Density-labeled 15 N (“heavy nitrogen”) and 14 N (“light nitrogen”) Procedure: 2 cultures, one of 15 NH 4 Cl, one of 14 NH 4 Cl 1 15 N strand(bottom of gradient) Transfer to 14 N medium F 1 : replication produces 2 15 N/ 14 N hybrid strand(middle of gradient) F 2 : replication again produces 2 15 N/ 14 N hybrid strands, 2 14 N strands(middle, top of gradient, respectively) Use DENSITY GRADIENT to differentiate 15 N from 14 N Extract DNA suspend DNA in CsCl solution ultracentrifuge density gradient DNA replication is unidirectional polymerization: 5’ 3’ (nucleotides added at 3’ end) Energy comes from breaking 2 of 3 dNTP phosphate groups (1 left for backbone)
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/17/2008 for the course BIO 121 taught by Professor Lampson,rea during the Fall '07 term at UPenn.

Page1 / 2

DNA Replication and Repair - DNA Replication and Repair(241...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online