So what is a DNA primer? Well, remember, a DNA primer is a relatively short sequence of DNA, so ranges from about 20 to 30 nucleotides. And what this is used for is to initiate the process of DNA synthesis, DNA replication. Number three, we need heat resistant DNA polymerase. So the reason we need a heat resistant one is because we're going to carry out the reaction at a relatively high temperature. Now, a DNA polymerase is needed because that's the protein complex that moves along that DNA and replicates that DNA.