Ultraviolet light

Definition

Ultraviolet light (UV light) is a form of electromagnetic radiation with wavelengths shorter than visible light but longer than X-rays, typically ranging from 10 nm to 400 nm. It plays a significant role in the induction of mutations at the molecular level, particularly in DNA, leading to various forms of radiation-induced mutations that can affect living organisms.

5 Must Know Facts For Your Next Test

1. UV light is divided into three categories: UVA (320-400 nm), UVB (280-320 nm), and UVC (100-280 nm), with UVC being the most damaging to DNA.
2. Exposure to UV light can cause specific types of DNA damage, such as pyrimidine dimers, which can disrupt normal base pairing and lead to errors during DNA replication.
3. The human skin's exposure to UV radiation is a major risk factor for developing skin cancers due to its ability to induce mutations in the cellular DNA.
4. Organisms have evolved various mechanisms to repair UV-induced DNA damage, including nucleotide excision repair and photoreactivation.
5. UV light is not only harmful but also has beneficial uses, such as sterilizing medical equipment and water by effectively killing bacteria and viruses.

Review Questions

• How does ultraviolet light contribute to the process of DNA damage, and what specific types of mutations can it cause?
  • Ultraviolet light causes DNA damage primarily through the formation of pyrimidine dimers, which occur when two adjacent thymine bases bond together instead of pairing with adenine. This type of mutation disrupts normal base pairing and can lead to errors during DNA replication. Over time, if these mutations are not repaired, they can accumulate and result in significant genetic alterations that may contribute to cancer development and other diseases.
• Discuss the different types of ultraviolet light and their respective roles in inducing radiation-induced mutations.
  • Ultraviolet light is classified into three types: UVA, UVB, and UVC. UVA has the longest wavelength and penetrates deeper into the skin, causing indirect DNA damage through the generation of reactive oxygen species. UVB is more energetic and primarily responsible for direct DNA damage through pyrimidine dimer formation. UVC is the most harmful but is mostly absorbed by the ozone layer. Each type has different effects on living organisms, with UVB being most directly linked to skin cancers due to its mutagenic potential.
• Evaluate the importance of repair mechanisms in mitigating the effects of ultraviolet light-induced mutations on human health.
  • Repair mechanisms such as nucleotide excision repair and photoreactivation are critical for maintaining genomic integrity after exposure to ultraviolet light. These systems recognize and correct UV-induced DNA lesions, reducing the likelihood of permanent mutations that could lead to diseases like cancer. The effectiveness of these repair pathways is vital for human health because any failure in these processes can result in the accumulation of mutations over time, significantly increasing cancer risk and other genetic disorders.

Related terms

DNA damage: The alteration or disruption of the DNA structure due to external factors, which can result in mutations and potentially lead to diseases such as cancer.

Mutagenesis: The process by which genetic information is changed, resulting in mutations; can be caused by chemical agents, radiation, or biological processes.

Photoreactivation: A light-dependent repair mechanism in some organisms that reverses UV-induced DNA damage by using visible light to restore normal DNA structure.