Ultraviolet light also referred to as UV light can be used as a germicidal agent to sterilize surfaces where sensitive microbiology techniques are being performed. UV light is nonionizing short wavelength radiation that falls between 4nm and 400nm in the visible spectrum. In general, the shorter the wavelength the more damaging it is to cells which makes UV light more damaging than visible light or infrared light. Most bacteria are killed by UV light. UV radiation at 260 nm is most damaging because at this wavelength DNA maximally absorbs UV light. When DNA absorbs UV light pyrimidine dimers form. A pyrimidine dimer is a covalent bond formed between two adjacent cytosine or thymine molecules in a DNA strand. These dimers distort the overall structure of the DNA strand and prevent DNA polymerase from moving past the dimer. Genes downstream from the dimer will not be transcribed and essential proteins will not be formed. The ability of the organism to function normally will be affected by the formation of one dimer.
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