Answer: ... in the UVB light exposure.
Explanation: When DNA is exposed to UVB radiation, thymine bases that are close to each other in the genetic sequence bond together, and this bond cannot be copied by the enzimes responsible for reproducing the genetic material. In the skin, it causes sunburns and stimulates the production of melanin. Luckily, DNA is only damaged by 0,1% of those UVB radiation photons, but even this percentege is enough to cause a sunburn anyway.
