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How can ultraviolet radiation damage DNA and lead to mutations?
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photochemical reaction
Chain of fluorescent tunicates.
Ultraviolet (UV) radiation damages DNA primarily through photochemical processes that alter the structure of genetic material, potentially leading to mutations if not corrected by cellular repair mechanisms.12
Mechanisms of DNA Damage
- Pyrimidine Dimerization: UV light can cause the covalent linking of adjacent pyrimidine bases (cytosine and thymine) within a DNA strand, creating structures known as pyrimidine dimers. These dimers distort the DNA double helix and physically block the replication machinery, preventing accurate copying of the genetic code.1342
- Photosensitization: UV radiation can facilitate photochemical processes where energy from a photon is transferred to molecular oxygen. This converts ground-state oxygen into highly reactive "singlet oxygen" or other free radicals, which can then chemically attack and oxidize DNA bases, such as guanine.12
From Damage to Mutation
If these lesions are not repaired, they can lead to mutations during DNA replication. Cells may attempt to bypass the damage through "translesion synthesis," an error-prone process that can introduce incorrect bases into the genetic sequence. If such mutations occur in growth-regulatory genes, they can contribute to the development of tumors and skin cancers, including melanoma.213