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Definition: How does the DNA mismatch repair system correct errors in DNA replication?

The DNA mismatch repair system is a crucial mechanism that corrects errors that occur during DNA replication. It ensures the fidelity of DNA replication by identifying and repairing mismatches or small insertions or deletions that may arise during the process.

Recognition of Mismatches

The first step in the DNA mismatch repair system is the recognition of mismatches. This process involves the identification of base-pairing errors or small indels (insertions or deletions) that occur during DNA replication. The recognition is facilitated by specific proteins, such as MutS and MutL, which can detect distortions in the DNA helix caused by mismatches.

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Excision of Mismatched DNA

Once a mismatch is recognized, the next step is the excision of the mismatched DNA. This process involves the removal of the incorrect nucleotide(s) from the newly synthesized DNA strand. The excision is carried out by a protein complex called MutHLS, which acts as an endonuclease to cleave the DNA strand near the mismatch.

Resynthesis and Ligation

After the mismatched DNA is excised, the next step is the resynthesis of the correct DNA sequence. This process is carried out by DNA polymerase, which synthesizes a new DNA strand complementary to the template strand. The newly synthesized DNA is then ligated to the adjacent DNA strand by DNA ligase, sealing the nick in the DNA backbone.

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Quality Control and Proofreading

The DNA mismatch repair system also plays a role in quality control and proofreading during DNA replication. It helps to prevent the incorporation of incorrect nucleotides into the newly synthesized DNA strand by removing mismatches before they become permanent mutations.

Overall, the DNA mismatch repair system is a vital mechanism that ensures the accuracy of DNA replication by correcting errors that occur during the process. It involves the recognition, excision, resynthesis, and ligation of mismatched DNA, ultimately maintaining the integrity of the genetic information.

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Keywords: mismatch, replication, strand, repair, system, during, mismatches, process, errors