Damage of DNA by ultraviolet radiation

The principal mechanism of DNA damage involves the photodimerization of adjacent thymine bases to yield either a cyclobutane-thymine dimer or a 6,4 photoproduct (Fig. 12.53). The former has been linked directly to cell death, and the latter may lead to DNA mutations and, consequently, to the formation of tumors. 

There are several natural mechanisms for protection from and repair of photochemical damage. For example, the enzyme DNA photolyase, present in organisms from all kingdoms but not in humans, catalyzes the destruction 

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Case study 128 Vision Case study 128 Photosynthesis Case study 12.4 Damage of DNA by ultraviolet radiation Case study 128 Photodynamic therapy... 

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