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Temperature-sensitive gene 43 mutants have been identified that have an antimutator phenotype, that is a lower rate of spontaneous mutation than wild type. [7] Studies of one of these mutants, tsB120, showed that the DNA polymerase specified by this mutant copies DNA templates at a slower rate than the wild-type polymerase. [8]
If the rate of DNA damage exceeds the capacity of the cell to repair it, the accumulation of errors can overwhelm the cell and result in early senescence, apoptosis, or cancer. Inherited diseases associated with faulty DNA repair functioning result in premature aging, [ 13 ] increased sensitivity to carcinogens and correspondingly increased ...
In order to preserve genetic information during cell division, DNA replication must be completed with high fidelity. In order to achieve this task, eukaryotic cells have proteins in place during certain points in the replication process that are able to detect any errors during DNA replication and are able to preserve genomic integrity.
DNA mismatch repair (MMR) is a system for recognizing and repairing erroneous insertion, deletion, and mis-incorporation of bases that can arise during DNA replication and recombination, as well as repairing some forms of DNA damage.
Multiple DNA polymerases have specialized roles in the DNA replication process. In E. coli, which replicates its entire genome from a single replication fork, the polymerase DNA Pol III is the enzyme primarily responsible for DNA replication and forms a replication complex with extremely high processivity.
The rate of DNA replication in a living cell was first measured as the rate of phage T4 DNA elongation in phage-infected E. coli. [24] During the period of exponential DNA increase at 37 °C, the rate was 749 nucleotides per second. The mutation rate per base pair per replication during phase T4 DNA synthesis is 1.7 per 10 8. [25]
Intrinsic termination (also called Rho-independent termination): Specific DNA nucleotide sequences signal the RNA polymerase to stop. The sequence is commonly a palindromic sequence that causes the strand to loop which stalls the RNA polymerase. [16] Generally, this type of termination follows the same standard procedure.
This rate is two orders of magnitude greater than the spontaneous rate of point mutation per nucleotide site in this species. [19] Older (indirect) studies reported locus-specific duplication rates in bacteria, Drosophila, and humans ranging from 10 −3 to 10 −7 /gene/generation. [20] [21] [22]