Mismatch repair

Definition

Mismatch repair is a cellular mechanism that corrects errors that occur during DNA replication, specifically when incorrect nucleotides are incorporated into the newly synthesized DNA strand. This process helps maintain the fidelity of genetic information by recognizing and removing mismatched base pairs, followed by the resynthesis of the correct sequence, thus playing a crucial role in preventing mutations.

5 Must Know Facts For Your Next Test

1. Mismatch repair is essential for correcting errors that escape the proofreading activity of DNA polymerase, significantly reducing the mutation rate.
2. The mismatch repair system can identify distortions in the DNA double helix caused by mispaired bases, allowing for targeted correction.
3. In E. coli, mismatch repair involves several key proteins, including MutS, MutL, and MutH, which work together to recognize and repair mismatches.
4. Deficiencies in mismatch repair mechanisms can lead to genetic disorders such as Lynch syndrome, which increases the risk of certain cancers.
5. The process is highly conserved across different organisms, indicating its fundamental importance in preserving genetic integrity.

Review Questions

• How does mismatch repair contribute to the accuracy of DNA replication?
  • Mismatch repair contributes to the accuracy of DNA replication by identifying and correcting errors made during the synthesis of new DNA strands. When incorrect nucleotides are incorporated, mismatch repair proteins detect these mismatches and initiate a series of actions to remove the erroneous bases and replace them with the correct ones. This mechanism significantly enhances the fidelity of DNA replication and helps prevent mutations that could lead to genetic disorders.
• Discuss the role of key proteins involved in mismatch repair and their specific functions.
  • Key proteins involved in mismatch repair include MutS, which recognizes mismatched base pairs; MutL, which acts as a mediator between MutS and other repair components; and MutH, which makes cuts in the DNA strand to allow for excision of the incorrect nucleotides. Together, these proteins coordinate the identification and repair of mismatches to ensure the integrity of the genetic information during DNA replication. Their interactions are crucial for initiating the repair process efficiently.
• Evaluate the implications of malfunctioning mismatch repair systems on human health and genetics.
  • Malfunctioning mismatch repair systems can lead to an increased rate of mutations, which has significant implications for human health. For example, individuals with deficiencies in this system may develop Lynch syndrome, a hereditary condition associated with a higher risk of various cancers due to uncorrected mutations. This highlights how essential mismatch repair is not only for maintaining genetic fidelity but also for preventing cancer and other genetic diseases. The broader impact on genetic diversity and evolution must also be considered, as unchecked mutations can lead to more rapid changes in populations.

Related terms

DNA polymerase:

An enzyme responsible for synthesizing new DNA strands by adding nucleotides to a growing chain during replication.

Exonuclease: An enzyme that removes nucleotides from the ends of a DNA strand, often involved in proofreading during DNA replication.

Mutations: Permanent alterations in the DNA sequence that can result from errors during replication, environmental factors, or other influences.