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DNA damage resulting in multiple broken chromosomes. DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. [1]
Nucleotide excision repair is a DNA repair mechanism. [2] DNA damage occurs constantly because of chemicals (e.g. intercalating agents ), radiation and other mutagens . Three excision repair pathways exist to repair single stranded DNA damage: Nucleotide excision repair (NER), base excision repair (BER), and DNA mismatch repair (MMR).
Eukaryotic DNA replication is a ... By repeating cycles of this process, DNA polymerase δ and ... Checkpoint proteins are also involved in some DNA repair pathways ...
Unlike bacteria, eukaryotic DNA replicates in the confines of the nucleus. [52] The G1/S checkpoint (restriction checkpoint) regulates whether eukaryotic cells enter the process of DNA replication and subsequent division. Cells that do not proceed through this checkpoint remain in the G0 stage and do not replicate their DNA. [citation needed]
This process is well-characterised in bacteria and much less well-characterised in many eukaryotes. In general, DNA repair enzymes complete the Okazaki fragments through a variety of means, including: base pair excision and 5' to 3' exonuclease activity that removes the chemically unstable ribonucleotides from the lagging duplex and replaces ...
Replication protein A (RPA) is the major protein that binds to single-stranded DNA (ssDNA) in eukaryotic cells. [1] [2] In vitro, RPA shows a much higher affinity for ssDNA than RNA or double-stranded DNA. [3] RPA is required in replication, recombination and repair processes such as nucleotide excision repair and homologous recombination.
Base excision repair (BER) is a cellular mechanism, studied in the fields of biochemistry and genetics, that repairs damaged DNA throughout the cell cycle. It is responsible primarily for removing small, non-helix-distorting base lesions from the genome.
The first column depicts mismatch repair in eukaryotes, while the second depicts repair in most bacteria. The third column shows mismatch repair, to be specific in E. coli. Micrograph showing loss of staining for MLH1 in colorectal adenocarcinoma in keeping with DNA mismatch repair (left of image) and benign colorectal mucosa (right of image).