Question

DNA polymerase III adds nucleotides ________?

1) to the 3' end of the RNA primer
2) to the 5' end of the RNA primer
3) in the place of the primer RNA after it is removed
4) to both ends of the RNA primer
5) to internal sites in the DNA template

Answer 1

DNA polymerase III adds nucleotides to the 3' end of the RNA primer, which is synthesized by RNA primase and provides the necessary free 3'-OH group for the elongation of the new DNA strand in a 5' to 3' direction.

Step-by-step explanation:

DNA polymerase III adds nucleotides to the 3' end of the RNA primer. During the process of DNA replication, it can only extend the new strand in a 5' to 3' direction, meaning it follows a downstream path guided by the free 3'-OH group. This enzyme needs a starting point, which is provided by the RNA primer synthesized by RNA primase. Once the primer is in place, DNA polymerase III can add DNA nucleotides one by one that are complementary to the template strand. Lastly, removal of the RNA primer and its replacement with DNA nucleotides is also crucial in this process, and is carried out by DNA polymerase I with the subsequent sealing of gaps by DNA ligase.