Ultraviolet (UV) radiation is mutagenic.
How do UV-induced DNA lesions lead to mutation?

Verified step by step guidance

1. Understand the nature of UV radiation: UV radiation is a form of electromagnetic radiation with wavelengths shorter than visible light. It is capable of causing damage to DNA by inducing chemical changes in the nucleotide bases.
2. Learn about UV-induced DNA lesions: UV radiation primarily causes the formation of pyrimidine dimers, such as thymine-thymine dimers or cytosine-thymine dimers. These lesions occur when adjacent pyrimidine bases on the same DNA strand become covalently bonded.
3. Explore the consequences of pyrimidine dimers: Pyrimidine dimers distort the DNA double helix structure, interfering with normal DNA replication and transcription processes. This can lead to errors during DNA synthesis.
4. Understand how mutations arise: If the DNA repair mechanisms, such as nucleotide excision repair, fail to correct the UV-induced lesions, DNA polymerase may insert incorrect bases opposite the damaged site during replication. This results in permanent changes to the DNA sequence, known as mutations.
5. Connect to broader implications: Mutations caused by UV radiation can lead to various outcomes, including cell death, malfunction, or uncontrolled cell growth (e.g., cancer). This highlights the importance of DNA repair systems in maintaining genomic integrity.

Key Concepts

UV Radiation and DNA Damage

Ultraviolet (UV) radiation can cause direct damage to DNA by inducing the formation of pyrimidine dimers, primarily thymine dimers. These dimers result from covalent bonding between adjacent thymine bases, disrupting the normal base pairing and leading to distortions in the DNA structure. If not repaired, these lesions can interfere with DNA replication and transcription.

DNA Repair Mechanisms

Cells have evolved several DNA repair mechanisms to correct UV-induced lesions, including nucleotide excision repair (NER) and photoreactivation. NER removes damaged sections of DNA and synthesizes new DNA to fill the gap, while photoreactivation directly reverses thymine dimers using light energy. Failure or inefficiency in these repair processes can lead to permanent mutations.

Mutation and Its Consequences

A mutation is a permanent alteration in the DNA sequence that can arise from unrepaired lesions. These mutations can lead to changes in protein function, potentially resulting in harmful effects such as cancer or genetic disorders. Understanding how UV-induced mutations occur is crucial for studying the mechanisms of carcinogenesis and the importance of DNA repair in maintaining genomic stability.