UV light particularly damages DNA below which wavelength?

Ultraviolet (UV) light is known to cause damage to DNA primarily in the range of wavelengths that can be absorbed by the nucleic acids, which include adenine, thymine, guanine, and cytosine. The most significant absorption occurs in the UV-C range, especially around 260-280 nm.

Choosing 320 nm (option B) as the wavelength above which DNA damage is particularly observed represents an important threshold. While 260 nm is often cited as the peak for DNA absorption and subsequent damage due to the formation of pyrimidine dimers, wavelengths around 280 nm still have enough energy to cause harmful interactions and mutations in DNA. As you move above 320 nm, the potential for direct DNA damage diminishes considerably, as the molecular absorption significantly decreases.

In contrast, wavelengths longer than 320 nm, like those found in the UV-A spectrum typically beyond 320 nm, possess less energy and do not interact with DNA in the same damaging way that UV-B and UV-C do. Consequently, the wavelength of 320 nm is often recognized as a critical point where significant DNA damage occurs, making it the appropriate choice in this context.