Question

Why is an intact, linear double helix an ineffective template for DNA polymerase?

a. It has a 3'-hydroxyl group, but lacks a template.
b. It lacks a 3'-hydroxyl group, but has a template.
c. It lacks a 3'-hydroxyl group and a template.
d. It has a 3'-hydroxyl group and has a template.
e. It lacks a 5'-hydroxyl group and has a template

Answer 1

An intact, linear double helix can't be used directly by DNA polymerase as it lacks a primer with a free 3'-OH group necessary to initiate DNA synthesis.

Step-by-step explanation:

An intact, linear double helix would be ineffective as a template for DNA polymerase because it cannot start the replication process on its own. DNA polymerase is an enzyme with specific requirements: it can only synthesize DNA in the 5' to 3' direction and needs a free 3'-hydroxyl group (3'-OH) to add nucleotides. This group is provided not by the intact double helix itself, but by a primer, which gives a starting point for DNA synthesis with an exposed 3'-OH end. Primers are short strands of RNA synthesized by an enzyme called RNA primase, which unlike DNA polymerases, does not require a pre-existing 3'-OH group. Once the primer is in place, DNA polymerase III can extend this primer with DNA nucleotides.