How Does DNA Polymerase I Add Nucleotides to the 3′ End of the RNA Primer?

How does DNA polymerase I function in DNA replication and what is its main role in the process?

Function of DNA Polymerase I in DNA Replication

DNA polymerase I is an essential enzyme involved in DNA replication. It plays a crucial role in extending the growing DNA strand by adding nucleotides to the 3′ end of the RNA primer, replacing it with DNA. This process is known as primer removal and DNA synthesis.

Main Role of DNA Polymerase I

The main function of DNA polymerase I in DNA replication is to add DNA nucleotides to the 3′ end of the RNA primer. The RNA primer is a short sequence of RNA that serves as a starting point for DNA synthesis. When DNA polymerase III displaces the RNA primer, DNA polymerase I removes it and replaces it with DNA nucleotides, thereby extending the growing DNA chain.

DNA Polymerase I: Step-by-Step Explanation

Here's a detailed step-by-step explanation of how DNA polymerase I adds nucleotides to the 3′ end of the RNA primer during DNA replication:

  1. DNA replication begins with the unwinding of the double-stranded DNA molecule.
  2. The enzyme called primase synthesizes a short RNA primer that binds to the template DNA strand.
  3. DNA polymerase III attaches to the RNA primer and starts adding DNA nucleotides to the 3′ end of the primer, forming a complementary DNA strand.
  4. As DNA polymerase III continues to move along the template DNA strand, it displaces the RNA primer.
  5. The displaced RNA primer is then removed by DNA polymerase I.
  6. DNA polymerase I adds DNA nucleotides to the 3′ end of the RNA primer, replacing it with DNA.
  7. This process is known as primer removal and DNA synthesis.
  8. DNA polymerase I continues adding DNA nucleotides to the 3′ end of the primer until it reaches the end of the template DNA strand.
  9. Simultaneously, DNA polymerase III continues synthesizing the complementary DNA strand by adding nucleotides to the 3′ end of the growing DNA chain.

By performing these steps, DNA polymerase I ensures the accurate replication and extension of the DNA strand during the DNA replication process.

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