in this video, we're going to talk about the steps of PCR, or polymerase chain reaction. And so PCR is actually a cyclical process that occurs in cycles where each of the cycles is going to have three steps that we have numbered down below. And so the very first step within each cycle is going to be the step of D natural ation, which is going to occur at high temperatures. The second step within each PCR cycle is going to be a kneeling, which is going to occur at low temperatures, and then the third and final step within each PCR cycle is going to be extension, which is going to occur at moderate temperatures. And so as we move forward in our course, we're going to talk about each of these three steps within each PCR cycle in more detail. But these three steps are going to be repeated in each PCR cycle, generating an exponentially growing number of DNA molecules and so down below. In this image, what we're showing you are the steps of PCR within just one cycle, and so at the very, very beginning, we're of course, going to have our reactant us and all of the four components that we talked about in our previous lesson videos, which includes the template D N A. The PCR primers, the heat resistant or thermo stable DNA preliminaries, tack, preliminaries and also the four nucleotides, the DNA nucleotides. Those would all be in part of the reactant within the test tube. And so, of course, it's going to include the template DNA, which is the gene of interest, which is what we're focusing on right here. And so in the very first step of the PCR cycle, we have DNA saturation, which is going to occur at higher temperatures. And so the D N A. Is going to be heated until the d n a d natures. And so the DNA maturation of the D. N A. Is going to separate the two strands of DNA, and so you can see that we have these flames here indicating the increase in temperature that is going to denature the D. N A. And separate the two strands. You can see that the hydrogen bonds have been broken and the two d N A strands have been separated, allowing each of those DNA strands to serve as a template. And so, in the second step of each PCR cycle, what we have is the process of a kneeling, and so this is going to occur at cooler temperatures. And so the DNA primers are going to bind with the single stranded DNA A at these cooler temperatures, and so you can see that now the DNA primers have bound to the DNA, and they are opposite Lee oriented and facing towards each other in terms of their five prime and three prime ends pointing towards each other. And so then we have the process of extension, which is going to occur at moderate temperatures. And so the heat resistant or the thermo stable DNA preliminaries called Tak preliminaries is going to build new D N A strands. And so it's going to be extending off of the primers and that five prime 23 prime direction for both strands and it will be building and amplifying the DNA. And so what we end up with are the products at the end of the first cycle of PCR, and so the gene of interest is going to have been amplified at the end of the PCR cycle and so you can see that now we have two copies. Two identical copies of the original gene of interest. And so again, this PCR, uh, steps. These PCR steps occur in cycles. And so these two here would be subject to the same process DNA creation and kneeling extension over and over and over again in these sets of cycles. And so again, we'll be able to talk about each of these steps within each cycle and more detail as we move forward in our course. But for now, this here concludes our brief introduction to the steps of PCR DNA saturation, a kneeling and extension, and I'll see you all in our next video.