DNA Replication Mechanism Explained

Overview of DNA Replication

DNA replication is a fundamental process in all living organisms, where a copy of the genetic information is made to pass on to the offspring. This process occurs during the S phase of the cell cycle and involves the duplication of the entire genome.

DNA replication is a complex process that involves various enzymes and proteins, each with specific roles in ensuring the accuracy and fidelity of the newly synthesized DNA strands.

Role of DNA Polymerase III

DNA polymerase III is the main enzyme responsible for synthesizing the new DNA strand during replication. It adds nucleotides to the 3' end of the RNA primer, which is essential for the elongation of the new DNA strand in a 5' to 3' direction.

DNA polymerase III follows the template strand and adds complementary nucleotides to it. This enzyme can only extend the new strand in a 5' to 3' direction, which means it must work in a downstream manner, guided by the free 3'-OH group provided by the RNA primer.

Synthesis Process

Before DNA polymerase III can start synthesizing the new DNA strand, a short RNA primer is synthesized by RNA primase. This primer provides the necessary free 3'-OH group for DNA polymerase III to add nucleotides and extend the new strand.

Once the RNA primer is in place, DNA polymerase III begins adding DNA nucleotides one by one, complementary to the template strand. This results in the formation of a new DNA strand that is an exact copy of the original template.

Primer Removal and Sealing of Gaps

After the DNA polymerase III has synthesized a new DNA strand, the RNA primer is no longer needed. DNA polymerase I removes the RNA primer and replaces it with DNA nucleotides, ensuring the continuity of the DNA strand.

Any gaps between the newly synthesized DNA fragments are sealed by DNA ligase, which helps in the complete replication of the DNA strand.

In conclusion, DNA polymerase III plays a vital role in adding nucleotides during DNA replication, ensuring the faithful duplication of the genetic material.