Mismatch repair

Definition

Mismatch repair is a critical cellular process that corrects errors that occur during DNA replication, specifically when the wrong nucleotide is incorporated into the newly synthesized strand. This mechanism is essential for maintaining genetic stability, as it prevents mutations that could lead to various diseases, including cancer. By recognizing and repairing these mismatched bases, the cell ensures the fidelity of genetic information passed on during cell division.

5 Must Know Facts For Your Next Test

1. Mismatch repair operates primarily through a complex of proteins that recognize and repair incorrectly paired nucleotides after DNA replication.
2. The process is highly specific and generally involves several steps: detection of the mismatch, excision of the erroneous section, and resynthesis using the correct template.
3. Deficiencies in mismatch repair can lead to increased mutation rates and are associated with hereditary nonpolyposis colorectal cancer (HNPCC), also known as Lynch syndrome.
4. Mismatch repair works alongside other DNA repair mechanisms, such as base excision repair and nucleotide excision repair, to maintain overall genomic integrity.
5. The fidelity of mismatch repair is enhanced by its ability to distinguish between the newly synthesized strand and the template strand, typically based on methylation patterns in prokaryotes.

Review Questions

• How does mismatch repair improve the accuracy of DNA replication?
  • Mismatch repair enhances the accuracy of DNA replication by identifying and correcting errors that occur when incorrect nucleotides are inserted. This process involves specialized proteins that detect mismatches, excise the incorrect nucleotides, and replace them with the correct ones using the complementary template strand. By fixing these errors shortly after replication, mismatch repair significantly reduces the likelihood of mutations being passed on to daughter cells.
• Discuss the consequences of deficiencies in mismatch repair systems in human health.
  • Deficiencies in mismatch repair systems can lead to a range of health issues, particularly an increased risk of developing certain types of cancer, such as Lynch syndrome, which predisposes individuals to colorectal and endometrial cancers. When mismatch repair mechanisms fail, it results in an accumulation of mutations within the genome. This not only contributes to tumorigenesis but also can affect the efficacy of treatments like chemotherapy, which rely on accurate DNA replication.
• Evaluate the role of mismatch repair in maintaining genomic stability and its interplay with other DNA repair mechanisms.
  • Mismatch repair plays a crucial role in maintaining genomic stability by correcting replication errors that could otherwise lead to harmful mutations. Its effectiveness is complemented by other DNA repair mechanisms such as base excision repair and nucleotide excision repair, which address different types of DNA damage. Together, these pathways form an intricate network that ensures cellular integrity and function; when one pathway is compromised, others may step in to mitigate potential damage, but reliance on backup systems can still lead to increased mutation rates if not adequately regulated.

Related terms

DNA Polymerase: An enzyme responsible for synthesizing new DNA strands by adding nucleotides complementary to the template strand during replication.

Exonuclease: An enzyme that removes nucleotides from the ends of a DNA strand, playing a role in proofreading and correcting mistakes during DNA synthesis.

Mutations: Permanent alterations in the DNA sequence that can arise from replication errors, environmental factors, or other cellular processes.