DNA damage from UV light
The purine and pyrimidine bases of nucleic acids absorb UV radiation strongly. UV light can be classified into three groups based on the wavelength: UV-A (315-400nm), UV-B (280-315nm) and UV-C (280 nm). UV light with longer wavelengths (UV-A and UV-B) affects DNA significantly.
The two main DNA lesions induced by UV-A and UV-B radiation are cyclobutane–pyrimidine dimers (CPDs) and 6–4 photoproducts (6–4PPs). These result in structural distortions which eventually lead to replication arrests and double-strand breaks.
Figure 1: UV induce nucleotide dimer.