Nucleotide excision repair (NER) is a DNA repair mechanism that removes bulky DNA lesions, such as those caused by ultraviolet (UV) radiation or chemical exposure. This process is crucial for maintaining genomic stability by correcting DNA damage that can lead to mutations, cancer, or other diseases. NER involves the recognition of damaged DNA, excision of the damaged strand, and synthesis of a new DNA strand to replace the removed section.
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Nucleotide excision repair is essential for fixing DNA damage that results from environmental factors like UV light and certain chemicals.
The NER pathway is highly conserved across various organisms, highlighting its importance in cellular health.
Defects in the NER mechanism can lead to disorders such as Xeroderma Pigmentosum, characterized by extreme sensitivity to sunlight and a higher risk of skin cancer.
NER works through several steps: damage recognition, strand incision, removal of the damaged segment, and DNA synthesis to fill in the gap.
The process involves multiple proteins and enzymes working together, including endonucleases, helicases, and DNA polymerases.
Review Questions
How does nucleotide excision repair identify and respond to DNA damage?
Nucleotide excision repair identifies DNA damage through specialized proteins that recognize distortions in the DNA helix caused by bulky lesions. Once damage is detected, these proteins signal for the recruitment of endonucleases that make incisions around the damaged area. This allows for the removal of the lesion along with some surrounding nucleotides before new DNA is synthesized to fill the gap, ensuring that the genetic information remains intact.
Discuss the implications of defective nucleotide excision repair on human health, particularly in relation to cancer risk.
Defective nucleotide excision repair can significantly increase the risk of developing skin cancer and other forms of cancer due to the accumulation of unrepaired DNA lesions. Conditions such as Xeroderma Pigmentosum arise from mutations in genes essential for NER, leading to extreme sensitivity to UV light and a dramatically higher incidence of skin tumors. This highlights the critical role that NER plays in protecting against mutagenic effects that can lead to carcinogenesis.
Evaluate how nucleotide excision repair contributes to cellular resilience against environmental stresses and its evolutionary significance.
Nucleotide excision repair contributes to cellular resilience by efficiently correcting DNA damage caused by environmental stresses like UV radiation and chemical exposure. This repair mechanism not only helps maintain genetic integrity but also reduces mutation rates, which is crucial for survival in changing environments. The evolutionary significance of NER lies in its ability to adaptively respond to potential threats, enabling organisms to thrive despite exposure to harmful agents, thereby enhancing their overall fitness and adaptability.
Related terms
DNA Polymerase: An enzyme responsible for synthesizing new strands of DNA during replication and repair processes.
Photoreactivation: A light-dependent repair mechanism that directly reverses DNA damage caused by UV radiation, specifically pyrimidine dimers.
Base Excision Repair: A DNA repair process that removes and replaces damaged or non-canonical bases in DNA.