In this video, we're going to focus on the first step of PCR, which is denaturation. In the very first step of the PCR cycle, heat is used to denature the DNA. We 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 of 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 helps break all of the hydrogen bonds or the H bonds between complementary base pairs in the DNA. Breaking these hydrogen bonds separates 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. Taq polymerase is able to withstand extremely high temperatures, but it is also able to withstand rapid temperature decreases as well. We will 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 of PCR.
In the very first step of PCR, we have denaturation. Within our test tube, we need to raise the temperature, and the heat denatures the complementary DNA strands. Denaturing the DNA means that the hydrogen bonds are broken and the DNA forms its single-stranded state. You can see we have two single-stranded DNA molecules here. Again, within this test tube, it is necessary to ensure that there is a thermostable polymerase. Over here, what we have is our thermostable polymerase with a name tag that says, "Hello, my name is Taq," because this is Taq polymerase. Notice that 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. I'll see you all in our next video.