Replication error rate during

Registiy of Mass Spectral Data, 412 Replication (DNA). 1106-1107 direction of, 1107 error rate during. 1107 lagging strand in, 1107 leading strand in, 1107 Okazaki fragments in, 1107 replication fork in, 1107 Replication fork (DNA), 1107 Reserpine, structure of, 65 Residue (protein), 1027 Resist, photolithography and, 505-506... 

Fig. 10-15 Organic carbon fluxes with depth in the water column normalized to mean annual primary production rates at the sites of sediment trap deployment. The undulating line indicates the base of the euphotic zone the horizontal error bars reflect variations in mean annual productivity as well as replicate flux measurements during the same season or over several seasons vertical error bars are depth ranges of several sediment trap deployments and uncertainities in the exact depth location. (Reproduced with permission from E. Suess (1980). Particulate organic carbon flux in the oceans - surface productivity and oxygen utilization, Nature 288 260-263, Macmillan Magazines.)...

Postreplicational mismatch repair has been found to correct errors in base substitution occurring during DNA replication in prokaryotes.48 This lowers the error rate for the polymerase from 1 in 106 to 107 to the observed range of values of 1 in 108 to 1010 in E. coli. How does the repair system know in this case which base in a mispair is the incorrect one The answer appears to be that the parent strand is tagged by methylation. A small proportion, some 0.2%, of the cytosine residues are methylated at the 5 position, and a similar proportion of the adenine residues are methylated at the 6 position. As methylation is a postreplicative event, the daughter strand is temporarily undermethylated after replication. 

A major goal of directed evolution of DNA polymerases has been to elucidate the structural elements that confer high fidelity during DNA replication. If DNA polymerases were to rely solely on the stability of nucleotides that aligned with template for discrimination of correct template-directed polymerization, the error frequency would be in the order of one mispaired nucleotide per 100 incorporated [23], The measured error rate for incorporation and extension of a mismatched nucleotide attributable to DNA polymerases lacking an error correcting exonucleolytic activity range... 

Errors and Repair. Errors occurring during replication could lead to deleterious mutations. However, many errors are corrected by enzyme activities associated with the complex at the replication fork. The error rate is thus kept at a very... 

A further aspect of specificity has become recognized in recent years, namely, proofreading. " The accurate replication of DNA during cell division is an event of crucial importance to an organism. DNA polymerases catalyze this process with an error rate of as little as 1 in This is achieved by a combination of Watson-Crick base pairing (error rate of the order of 1 in (/) in combination with a proofreading step in which checks are made after the addition of each base to the 3 end of the growing DNA chain that the correct pair was formed. Any incorrectly added bases are removed by a 3 -5 exonucle-ase activity that occurs at an active site distinct from the polymerase site. 

During the process of DNA replication, the normal rate of error is remarkably low, but errors still occur. Consequently, the cell has a system for repairing errors (Fig. 6.46) occurring during cell division when chromosomal DNA sequences are replicated by one of a series of polymerases. This is carried out by mismatch repair enzymes, which monitor and detect miscopied new DNA sequences. However, these repair processes are generally for normal bases put in the wrong place or the wrong number of bases in a repeat sequence. 

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