This video we're going to focus on the first step of PCR, which is denaturation. In the very first step of PCR cycle, heat is going to be used to denature the DNA. We're going to heat denature the double-stranded DNA in order to convert the DNA into its single-stranded form. Each of the single-stranded DNA molecules can serve as a template for a new molecule DNA. The temperature of the PCR mixture is going to be increased to about 95 degrees Celsius, which is very near boiling temperatures. Increasing the temperature to 95 degrees Celsius is going to help break all of the hydrogen bonds between complementary base pairs in the DNA. Breaking those hydrogen bonds is going to separate the double-stranded DNA into its single-stranded form.

It's very important that a special thermostable DNA polymerase, such as Taq polymerase, is used in the PCR mixture. This Taq polymerase does not denature at the high temperatures used in PCR. The Taq polymerase is able to withstand extremely high temperatures, but it's also able to withstand rapid temperature decreases as well. We're going to see rapid temperature decreases in the second step of PCR. However, it's also important to note that although Taq polymerase can withstand high temperatures and rapid temperature decreases, it does not actually synthesize DNA unless it is at an ideal temperature. This will be important once we get to the third step.

In the very first step of PCR, what we have is denaturation. Within our test tube, we're going to have our DNA, and we'll need to raise the temperature, which you can see these flames here are going to raise the temperature, and the heat is going to denature. So the heat denatures the complementary DNA strands, and denaturing the DNA really just means that the hydrogen bonds are going to be broken and the DNA is going to be forming its single-stranded form. So you can see we have two single-stranded DNA molecules here.

Again, within this test tube, we need to ensure that there is a thermostable polymerase. Over here, we have our thermostable polymerase here. You can see he’s got this name tag that says, hello, my name is Taq, because this is Taq polymerase. Notice that Taq polymerase has no problems with the heat. The heat never bothered him anyway. Taq polymerase is going to be very important to have and use during PCR.

This here concludes our introduction to the first step of PCR denaturation. As we move forward, we'll be able to talk about the second and third steps of PCR. So I’ll see you all in our next video.