Abstract:

The deoxyribonucleic acid (DNA) of living organisms is damaged by exogenous and endogenous agents. These damages are repaired by a series of repair mechanisms. These repair mechanisms function both directly and indirectly. Photoreactivation, repair by O6-methylguanineDNA-methyltransferase, base-excision repair, nucleotide-excision repair, DNA double-strand break repair, homologous recombination repair, non-homologous end-joining, and mismatch repair are some examples of these mechanisms. Many damages, such as DNA strand breakage in the genome and base-base mismatches during replication, are repaired by various repair systems. There are some anomalies and disorders that develop when damage cannot be repaired or when the repair processes are impaired. These include xeroderma pigmentosum, Cockayne syndrome, Bloom syndrome, Werner syndrome, Huntington's disease, ataxia-telangiectasia, Nijmegen breakage syndrome, and Fanconi anemia. The functioning of DNA repair systems and the diseases caused by their defects are discussed in this review.

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