Scientists in the US have developed a way to control DNA amplification by switching it on and off with UV light.The polymerase chain reaction (PCR) is widely used to amplify small amounts of DNA by repeatedly copying the nucleic acid sequence. A polymerase enzyme builds the copies onto short strands of DNA called primers. To control the PCR, Alexander Deiters from North Carolina State University, Raleigh, and his colleagues incorporated bulky protecting groups called cages into the primers, preventing the copying process. Deiters explained: 'The presence of the cagesd distributed evenly through the primer is sufficientto prevent its annealing to the DNA template and its amplification.' Shining UV light on the caging groups removes them and enables PCR to start.
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