Question

DNA polymerases catalyze the production of polynucleotide chains. Which of the following statements holds true:

A. DNA polymerases do not require a primer in order to initiate the reaction
B. DNA polymerases require a primer with a free 5'-end
C. DNA polymerases require a primer base-paired to the template with a free 5'-end
D. DNA polymerases require a RNA primer base-paired to the template and with a free 3'-end.
E. DNA polymerases require a DNA primer base-paired to the template and with a free 5'-end.

Answer 1

DNA polymerases require a RNA primer with a free 3'-end that is base-paired to the template to initiate DNA synthesis.

Step-by-step explanation:

Regarding the statement about DNA polymerases and their requirement for initiating a reaction, the correct statement is D. DNA polymerases require a RNA primer base-paired to the template and with a free 3'-end. DNA polymerases are unable to start the synthesis of a new DNA strand from scratch. They can only add to a pre-existing nucleic acid strand by attaching nucleotides to the free 3'-OH group. This is achieved through the action of RNA primase, which synthesizes a short RNA primer that is complementary to the DNA template to provide the necessary 3'-OH end. Once the primer is in place, DNA polymerase extends this primer, adding DNA nucleotides one by one to synthesize the new strand.