In this lesson, you will learn about the important enzyme DNA polymerase and the role it plays in the process of DNA replication. When you are through, test your understanding with a brief quiz.
What Is DNA Polymerase?
Our body is composed of millions of cells that contain their own copy of our DNA.
The amazing thing is that we all started out as one cell with the original copy of our DNA. From that one cell, other cells were produced, and each received a copy of the DNA. So, how did this amazing thing happen? Well, just before a cell splits into two cells, the DNA is copied in a process known as DNA replication.
There is replication machinery which includes the enzyme DNA polymerase. DNA polymerase has the responsibility of creating new copies of our DNA. Let’s take a closer look at how this happens.
Function of DNA Polymerase
Before DNA polymerase can start copying the DNA, it has to have access to the nucleotide bases that compose the DNA.
Our DNA is made of two strands of DNA that are connected to each other by hydrogen bonds. As you may recall, our DNA is normally in the double-helix formation, which looks a lot like a winding staircase. In order for the nucleotides to be exposed, DNA helicase comes in and unwinds the DNA by breaking the hydrogen bonds that hold the two strands together.
This allows the nucleotides on both strands of DNA to be read and used as templates by DNA polymerase. The next thing that has to happen is that an RNA primer attaches complementary nucleotide bases, which starts the process of replication on both strands. An RNA primer is essentially just a short strand of RNA bases, usually around 20 bases long, that is needed by DNA polymerase to start replication.
Now DNA polymerase is ready to go to work. DNA polymerase will use the template strands as a guide to attach the bases that are complementary on the newly synthesized strand of DNA. The nucleotides are added to the 3’OH end of the previous nucleotide.DNA polymerase will synthesize the DNA in the 5′ to 3′ direction. This will continue down the length of both of the single strands of DNA. Once the process is complete, DNA polymerase will have made a copy of the DNA. Each copy of DNA will be semiconservative, meaning that it will contain one of the template strands as well as one of the newly synthesized strands of DNA.
In summary, we have covered what DNA polymerase is and what it does. DNA polymerase is an enzyme that synthesizes new copies of DNA. It carries out this function after DNA helicase has unzipped the DNA, thereby creating two single strands of DNA that can be used as templates. DNA polymerase adds nucleotides onto the 3’OH end of the preceding nucleotide and carries out synthesis in the 5′ to 3′ direction down the length of the DNA. The result of DNA polymerase function is two copies of DNA that contain one original and one newly synthesized strand of DNA.