Semi-Conservative Replication
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Semiconservative replication describes the mechanism of DNA replication in all known cells. It derives its name from the production of two copies of the original DNA molecule, each of which contains one original strand, and one newly-synthesized strand. [1][2]
The structure of DNA (as deciphered by James D. Watson and Francis 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 and is supported by the Meselson-Stahl experiment[2][3]
Semi-Conservative Replication
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Semiconservative replication describes the mechanism of DNA replication in all known cells. It derives its name from the production of two copies of the original DNA molecule, each of which contains one original strand, and one newly-synthesized strand. The structure of DNA (as deciphered by James D. Watson and Francis 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.
Different experiments were conducted to determine how DNA replicates. The semiconservative model was anticipated by Nikolai Koltsov, and is supported by the Meselson-Stahl experiment[2][3]. Meselson- Stahl confirmed that DNA replicated semi-conservatively by conducting an experiment using two radioisotopes→ nitrogen-15 (15N) and nitrogen-14 (14N). When 14N was added to the 15N-15N heavy DNA, a hybrid of 15N-14N was seen in the first generation. After the second generation, the hybrid remained, but light DNA (14N-14N) was seen as well. This indicated that DNA replicated semi-conservatively. This model of replication seemed most reasonable since it would allow each daughter strand to remain associated with its template strand.[1]
Further Applications and Advantages
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Semiconservative replication provides many advantages for DNA. It is not only fast and accurate[2], but it has been found to allow DNA to be repaired easily and is responsible for phenotypic diversity in a few prokaryotic species. The process of creating a newly synthesized strand from the template strand allows for the old strand to be methylated at a separate time from the new strand. This allows repair enzymes to proofread the new strand and correct any mutations or errors[3].
DNA could have the ability to activate or deactivate certain areas on the newly synthesized strand that allows it to change the phenotype of the cell. This could be advantageous for the cell because it could activate a more favorable phenotype to aid in survival. Due to Natural selection, the more favorable phenotype would persist throughout the species. This gives rise to the idea of inheritance, or why certain phenotypes are inherited over another[3].
- ^ Hanawalt, P. C. (2004-12-17). "Density matters: The semiconservative replication of DNA". Proceedings of the National Academy of Sciences. 101 (52): 17889–17894. doi:10.1073/pnas.0407539101. ISSN 0027-8424.
- ^ McCarthy, David; Minner, Charles; Bernstein, Harris; Bernstein, Carol (1976-10). "DNA elongation rates and growing point distributions of wild-type phage T4 and a DNA-delay amber mutant". Journal of Molecular Biology. 106 (4): 963–981. doi:10.1016/0022-2836(76)90346-6. ISSN 0022-2836.
{{cite journal}}: Check date values in:|date=(help) - ^ a b Norris, Vic (2019-04-01). "Does the Semiconservative Nature of DNA Replication Facilitate Coherent Phenotypic Diversity?". Journal of Bacteriology. 201 (12). doi:10.1128/jb.00119-19. ISSN 0021-9193.