Semiconservative replication

Semiconservative replication describes the mechanism of DNA replication in all known cells. It derives its name from the fact that it produces two copies of the original DNA molecule, each of which contains one of original strand, and one newly-synthesized strand. Semiconservative replication describes the mechanism of DNA replication in all known cells. It derives its name from the fact that it produces two copies of the original DNA molecule, each of which contains one of original strand, and one newly-synthesized strand. The structure of DNA (as deciphered by Watson and Crick in 1953) suggested that each strand of the double helix would serve as a template for synthesis of a new strand. However, it was not known how newly synthesized strands combined with template strands to form two double helical DNA molecules. The semiconservative model of replication seemed most reasonable since it would allow each daughter strand to remain associated with its template strand. The semiconservative model was anticipated by Nikolai Koltsov, is supported by the Meselson-Stahl experiment as well as subsequent experiments that enabled autoradiographic visualization of the distribution of old and new strands within replicated chromosomes. Experimental evidence confirmed that two lines were observed, therefore offering compelling evidence for the semi-conservative theory. Semiconservative replication derives its name from the fact that this mechanism of transcription was one of three models originally proposed for DNA replication: The rate of semiconservative DNA replication in a living cell was first measured as the rate of phage T4 DNA strand elongation in phage-infected E. coli. During the period of exponential DNA increase at 37 °C, the rate of strand elongation was 749 nucleotides per second. The mutation rate per base pair per round of replication during phage T4 DNA synthesis is 2.4×10−8. Thus semiconservative DNA replication is both rapid and accurate.