Which exposure causes the formation of thymidine dimers in the skin?

Thymidine dimers are formed when DNA is exposed to ultraviolet (UV) light, particularly UVB radiation. This type of exposure leads to the covalent bonding of adjacent thymine bases in the DNA strand, resulting in the formation of these dimers. This specific DNA damage can interfere with normal DNA replication and transcription, potentially leading to mutations if not adequately repaired.

The skin is particularly susceptible to UVB light, which is prevalent in sunlight. When the skin is exposed to this type of UV radiation, it can cause direct damage to the DNA in skin cells, which is a primary mechanism through which UV radiation contributes to skin cancers, including melanoma and non-melanoma types.

Understanding the specific effects of UVB highlights its role as a carcinogen and explains why protective measures against sun exposure are important for skin health.