What process is a thermocycler primarily used for?

A thermocycler is primarily used for the polymerase chain reaction (PCR), a technique that allows the amplification of specific segments of DNA. During PCR, the thermocycler rapidly changes temperatures to facilitate the denaturation of DNA, annealing of primers, and extension by DNA polymerase. This cycling of temperatures is crucial for the success of the amplification process, allowing for millions of copies of a DNA fragment to be generated from a small initial sample.

This ability to simultaneously manage precise temperature control in different cycles makes the thermocycler an essential tool in molecular biology laboratories for applications such as cloning, gene expression analysis, and genetic diagnostics. The other options, while related to DNA and proteins, do not utilize the thermocycling process in the same way that PCR does.