What structural change occurs in DNA as a result of UV light exposure?

When DNA is exposed to UV light, one of the significant structural changes that can occur is the formation of covalent bonds between adjacent thymine bases on the same strand. This results in the creation of thymine dimers. The formation of these dimers disrupts normal base pairing and can lead to mutations if not repaired.

This process is highly relevant in the context of DNA repair mechanisms, as cells have to address the mutations caused by UV-induced damage. While the other options hint at possible alterations in DNA behavior or interactions, they do not specifically align with the well-established and documented effects of UV light on DNA structure. Therefore, the pairing of thymine bases with one another due to UV exposure is a critical phenomenon, as it highlights the impact of environmental factors on genetic integrity.