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Because there is a small probability of recombination at any location along a chromosome, the frequency of recombination between two locations depends on the distance separating them. [citation needed] Therefore, for genes sufficiently distant on the same chromosome, the amount of crossover is high enough to destroy the correlation between alleles.
Once the template becomes discontinuous, it will create an Okazaki fragment. Defects in the maturation of Okazaki fragments can potentially cause strands in the DNA to break and cause different forms of chromosome abnormality. These mutations in the chromosomes can affect the appearance, the number of sets, or the number of individual chromosomes.
8-oxoguanine forms a Hoogsteen base pair with adenine. Single bases in DNA can be chemically damaged by a variety of mechanisms, the most common ones being deamination, oxidation, and alkylation. These modifications can affect the ability of the base to hydrogen-bond, resulting in incorrect base-pairing, and, as a consequence, mutations in the DNA.
Examples of mismatched bases include a G/T or A/C pairing (see DNA repair). Mismatches are commonly due to tautomerization of bases during DNA replication. The damage is repaired by recognition of the deformity caused by the mismatch, determining the template and non-template strand, and excising the wrongly incorporated base and replacing it ...
Similarly, the MMR pathway only targets mismatched Watson-Crick base pairs. Nucleotide excision repair (NER) is a particularly important excision mechanism that removes DNA damage induced by ultraviolet light (UV). UV DNA damage results in bulky DNA adducts — these adducts are mostly thymine dimers and 6,4-photoproducts. Recognition of the ...
Furthermore, DNA polymerase III must be able to distinguish between correctly paired bases and incorrectly paired bases. This is accomplished by distinguishing Watson-Crick base pairs through the use of an active site pocket that is complementary in shape to the structure of correctly paired nucleotides.
Base excision repair (BER): damaged single bases or nucleotides are most commonly repaired by removing the base or the nucleotide involved and then inserting the correct base or nucleotide. In base excision repair, a glycosylase [ 22 ] enzyme removes the damaged base from the DNA by cleaving the bond between the base and the deoxyribose.
dnaQ is the gene encoding the ε subunit of DNA polymerase III in Escherichia coli. [1] The ε subunit is one of three core proteins in the DNA polymerase complex. It functions as a 3’→5’ DNA directed proofreading exonuclease that removes incorrectly incorporated bases during replication.