Ultraviolet radiation

Definition

Ultraviolet radiation is a form of electromagnetic radiation that comes primarily from the sun and has wavelengths shorter than visible light but longer than X-rays. It plays a significant role in biological processes, particularly in the induction of mutations in DNA, which is crucial to understanding how genetic changes can occur due to environmental factors.

5 Must Know Facts For Your Next Test

1. Ultraviolet radiation is divided into three types: UVA, UVB, and UVC, with UVB being the most damaging to DNA and associated with sunburn and skin cancer.
2. Exposure to UV radiation can lead to the formation of pyrimidine dimers in DNA, which can disrupt normal base pairing and result in mutations.
3. Cells have developed various mechanisms, such as nucleotide excision repair, to fix the damage caused by UV radiation.
4. While UV radiation can cause harmful mutations, it also plays a role in vitamin D synthesis, which is essential for bone health.
5. In addition to its effects on humans, UV radiation can also influence the evolution of microorganisms and other organisms through induced mutations.

Review Questions

• What types of DNA damage are caused by ultraviolet radiation, and how do they affect genetic integrity?
  • Ultraviolet radiation causes several types of DNA damage, primarily forming pyrimidine dimers where two adjacent thymine bases bond together incorrectly. This alteration disrupts normal base pairing during DNA replication and can lead to mutations if not repaired. If these mutations occur in critical genes, such as tumor suppressor genes, they can compromise genetic integrity and increase the risk of diseases like cancer.
• Discuss the cellular mechanisms that organisms use to repair DNA damage induced by ultraviolet radiation.
  • Organisms utilize several cellular mechanisms to repair DNA damage from ultraviolet radiation. One key mechanism is nucleotide excision repair (NER), which identifies and removes damaged sections of DNA, replacing them with the correct nucleotides. Another mechanism is photoreactivation, which uses light energy to directly reverse the formation of pyrimidine dimers. These repair processes are crucial for maintaining genomic stability and preventing the accumulation of potentially harmful mutations.
• Evaluate the dual role of ultraviolet radiation in both causing mutations and facilitating beneficial processes like vitamin D synthesis.
  • Ultraviolet radiation has a complex role as it induces harmful mutations while also enabling beneficial biological processes such as vitamin D synthesis. On one hand, excessive exposure can lead to significant DNA damage and increase cancer risk; on the other hand, UV radiation stimulates the production of vitamin D in the skin, essential for maintaining healthy bones and immune function. This duality highlights the importance of moderation in sun exposure, balancing the need for vitamin D with the risks associated with UV-induced mutations.

Related terms

DNA damage: The alteration of the DNA structure, often caused by external agents like UV radiation, leading to mutations and potential cell dysfunction.

Photoreactivation: A light-dependent repair mechanism in cells that can reverse certain types of DNA damage caused by ultraviolet radiation.

Melanin: A pigment produced by skin cells that provides some protection against UV radiation by absorbing harmful rays and preventing DNA damage.