Nucleotide excision repair

Definition

Nucleotide excision repair (NER) is a DNA repair mechanism that identifies and removes damaged or mismatched nucleotides in the DNA strand. This process is crucial for maintaining genetic stability, as it corrects various types of DNA lesions, particularly those caused by environmental factors like UV radiation and chemical exposure. By repairing these lesions, NER helps to prevent mutations and genetic variations that could lead to diseases, including cancer.

5 Must Know Facts For Your Next Test

1. Nucleotide excision repair involves several key steps: damage recognition, nucleotide removal, DNA synthesis to fill the gap, and ligation to restore the DNA strand's integrity.
2. NER is particularly effective at repairing bulky adducts and helix-distorting lesions that can arise from UV light exposure or certain chemicals.
3. Defects in the nucleotide excision repair pathway are linked to genetic disorders such as Xeroderma Pigmentosum, which increases skin cancer risk due to UV sensitivity.
4. NER operates in a coordinated manner involving multiple proteins, including helicases, endonucleases, and DNA ligases, to execute its functions.
5. The efficiency of nucleotide excision repair can be influenced by factors like age, environmental conditions, and individual genetic variations.

Review Questions

• How does nucleotide excision repair contribute to genetic stability, and what are some types of damage it specifically targets?
  • Nucleotide excision repair plays a vital role in maintaining genetic stability by identifying and repairing a range of DNA damages, particularly those that cause distortion of the DNA helix. It specifically targets bulky lesions such as those caused by UV radiation or chemical agents. By removing these damaged nucleotides and synthesizing new ones, NER prevents the propagation of mutations that could lead to serious health issues like cancer.
• Discuss the implications of defective nucleotide excision repair systems on human health, particularly in relation to specific diseases.
  • Defective nucleotide excision repair systems can lead to increased susceptibility to various diseases due to the accumulation of uncorrected DNA damage. For example, individuals with Xeroderma Pigmentosum have impaired NER capabilities, resulting in extreme sensitivity to UV light and a significantly heightened risk of developing skin cancers. These health implications highlight the importance of NER in protecting against genotoxic stress from environmental factors.
• Evaluate the broader impact of nucleotide excision repair mechanisms on evolution and genetic variation within populations.
  • Nucleotide excision repair mechanisms play a crucial role in shaping evolutionary dynamics by maintaining the integrity of an organism's genome. Efficient NER helps reduce the mutation rate by correcting damage before it can be replicated, thus promoting genetic stability within populations. However, variations in NER efficiency among individuals can contribute to differences in mutation rates and genetic diversity, influencing evolutionary processes. Over time, this can lead to adaptations or susceptibilities within populations based on their ability to effectively manage environmental stresses.

Related terms

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

mutagen: An agent that causes changes in the DNA sequence, potentially leading to mutations; common examples include chemicals and radiation.

base excision repair: A DNA repair mechanism that removes and replaces damaged or incorrect bases in the DNA, addressing smaller scale lesions compared to NER.