The process of electrophoresis
Remember gel electrophoresis is the separation of molecules according to their size and charge (negatively charged DNA molecules move to the positive pole). Examiners like to ask questions about gel electrophoresis, so make sure you understand each of the different steps in the process.
Target DNA sequences can be copied exponentially by PCR to generate billions of copies in a short time
You don't need to know the detail of the three stages and the temperatures the reactions occur at during the different stages. However, you must know why the Taq polymerase is used in PCR (from Topic 2.6.3). The main learning point is that PCR can be used to amplify very small amounts of DNA into large numbers of molecules for analysis.