N-15N Bottom I0 generation The meselson Stahl experiment: DNA molecules AI generation duplicate semiconservative in E coli cells 白2 generations 白3 generations A 4 generations - 0 and 2 mixed e0 and 4 mixed 14N-14N15N-14N15N-5N
The MeselsonStahl experiment: DNA molecules duplicate semiconservatively in E. coli cells. 15N- 15N 0 generation 1 generation 2 generations 3 generations 4 generations 0 and 2 mixed 0 and 4 mixed 15N- 14N 15N- 14N- 14N 15N Top Bottom
3. A variety of simple questions were asked about DNA replication Are the two parental strands completely unwound before replication begins Does replication begin at random sites or at unique sites Does DNA replication proceed in one direction or both directions? The overall chain growth occurs in 5-3,35,or both directions? What mechanisms ensure that DNA replicates once per cell division?
3. A variety of simple questions were asked about DNA replication • Are the two parental strands completely unwound before replication begins? • Does replication begin at random sites or at unique sites? • Does DNA replication proceed in one direction or both directions? • The overall chain growth occurs in 5` 3`, 3` 5`, or both directions? • What mechanisms ensure that DNA replicates once per cell division?
What enzymes take part in DNA synthesis? How does duplication of the long helical duplex occur without the strands becoming tangled?
• What enzymes take part in DNA synthesis? • How does duplication of the long helical duplex occur without the strands becoming tangled? …
4. Autoradiography studies: daughter strands are synthesized immediately after parental strands separate Electron micrographs of the autoradiographs of replicating plasmid, SV40 virus, and E coli chromosomal DNA with 3H-thymidine incorporated revealed @-like structures: no single stranded DNa was visible The chromosomal DNA of coli is a single huge circle! No temporary creation of linear DNA occurred during replication of the circular dNa
4. Autoradiography studies: daughter strands are synthesized immediately after parental strands separate • Electron micrographs of the autoradiographs of replicating plasmid, SV40 virus, and E. coli chromosomal DNA with 3H-thymidine incorporated revealed -like structures: no single stranded DNA was visible. • The chromosomal DNA of E. coli is a single huge circle! • No temporary creation of linear DNA occurred during replication of the circular DNA
A electron micrograph of the replication intermediate of a plasmid DNA: 6-shaped structures were observed: no single stranded dNA is visible No complete unwinding of the two parental strands occurred before the daughter strands are synthesized
A electron micrograph of the replication intermediate of a plasmid DNA: -shaped structures were observed; no single stranded DNA is visible. No complete unwinding of the two parental strands occurred before the daughter strands are synthesized