radiation exposure article 86 metabolism 40 Ultraviolet Rays 38 ultraviolet radiation 34 Light 32 light 32 Animals 26 Humans 26 animal 24 chemistry 24 human 24 physiology 24 controlled study 22 drug effect 20 growth, development and aging 20 Time Factors 18 time 18 DNA Damage 16 priority journal 16 radiation response 16 DNA 14 DNA damage 14 genetics 14 human cell 14 Cell Line 12 DNA repair 12 cell line 12 gene expression regulation 12 Apoptosis 10