Question

Why does DNA polymerase require a primer?

(A) The primer provides a 5' phosphate group
(B) The primer provides a 3' OH group
(C) The primer acts as a template for replication
(D) All of the above

Answer 1

DNA polymerase requires a primer to provide a free 3'-OH group, which is essential for the enzyme to add nucleotides and synthesize a new DNA strand during replication.

Step-by-step explanation:

DNA polymerase requires a primer because it can only add nucleotides to a pre-existing strand that provides a free 3'-OH group. The correct answer to why DNA polymerase requires a primer is (B) The primer provides a 3' OH group. A primer is a short RNA strand synthesized by RNA primase on the template DNA, which makes it possible for DNA polymerase to start the synthesis of a new DNA strand during DNA replication. Unlike DNA polymerase, RNA primase can start synthesis from scratch without the need for a primer, providing the crucial 3'-OH group that DNA polymerase needs to form phosphodiester bonds and extend the DNA strand.