Either for school or your own curiosity, you may wonder exactly how DNA replicates itself. DNA replication is essentially the process by which DNA copies itself to form another cell. This is something that is occurring all of the time in your body at incredible speeds. There are three main steps.
Replication of DNA begins at the site of origin called “oriC.” It is here that initiator proteins bind to the origin and cause the DNA strands to unwind. This is performed by an enzyme known as helicase. Other proteins keep the two strands from winding themselves together again. In order to move to the next step of replication, the cell creates RNA primers which are a starting point for the next step.
As mentioned before, the RNA primer is used as a starting point for the leading strand. The strand itself acts as a template for the new DNA strand. There are four nucleotide bases in DNA–A, T, G, C. They have specific pairing rules. A only binds with T. G only binds with C, except for certain cases. These all possess genetic information when combined. Let’s say the template strand has the following bases in this order: AGTC. Then the new strand that is created from the template strand is: TCAG. The DNA Polymerase is the molecule responsible for running down the template strand and adding the new bases. The same polymerase is also responsible for proofreading to ensure that every base is connected properly.
This is all performed for the leading strand. The lagging strand is a bit different. Instead of one long and continuous strand, the lagging strand is actually cut up into different pieces which are later all connected. These fragments are Okazaki fragments.
Once all the bases have been added, the primers are removed, additional bases are placed into the gaps, and the DNA strand proceeds to the final step of replication.
With the proofreading finished and all of the fragments joined together, DNA ligase seals the two sequences and you have yourself two continuous double strands. You are left with a brand new DNA strand that contains one old strand and one brand new strand. The DNA winds back up into the familiar double helix shape, and the cell has its genetic information intact.
One last interesting feature of termination is the role of telomerase. This molecule is responsible for ensuring that the strand doesn’t shorten prematurely. It adds on additional bases to prevent this. Because shortening strands have been linked to aging, telomerase’s role in DNA replication has been suggested to help with anti-aging in humans. A cure for aging?