Medically important form of UV radiation is:(LQ)
1). Pyrimidine dimers are produced as a result of the absorption of UV-B by DNA. These structural changes are repaired by mechanisms that result in their recognition, excision, and the re-establishment of normal base sequences.
2). The repair of these structural changes is crucial, because individuals with defective DNA repair are at high risk for the development of cutaneous cancer.
3). Patients with xeroderma pigmentosum are characterized by decreased repair of UV-induced photoproducts, as a result their skin develop the xerotic appearance of photo-aging as well as basal cell and squamous cell carcinomas and melanoma in the first two decades of life.