Thymine Dimers are Caused By

Question

Thymine dimers are caused by
A) X-rays.
B) free radicals such as oxygen.
C) EMS or NSG.
D) depurination.
E) UV light.

Accepted Answer

Thymine dimers are formed by the covalent linkage of adjacent thymine bases in DNA when it is exposed to UV radiation, specifically the 254-nm wavelength of UV light. The energy from the UV light causes a rearrangement of the chemical bonds in the thymine bases, creating a covalent bond between the two adjacent thymines, which distorts the DNA structure and impairs DNA replication and transcription. The other options, including X-rays, free radicals, chemicals like EMS or NSG, and depurination, can cause DNA damage, but they do not directly lead to the formation of thymine dimers.