Question

Which of the following is a reason why sticky end producing restriction enzymes are preferred compared to blunt end ones?

A) Because sticky ends created by any restriction enzymes can be ligated to sticky ends created by any other restriction enzyme.
B) Because sticky ends are more amenable to the mechanism of phosphodiester bond formation by DNA ligase.
C) Because blunt ends can be mistaken as double stranded breaks which are degraded by DNA repair pathways.
D) Because sticky ends can be temporarily held together by hydrogen bonding between the two strands.
E) Because blunt ends can be temporarily held together by hydrogen bonding between the two strands.

Answer 1

D) Because sticky ends can be temporarily held together by hydrogen bonding between the two strands.

Step-by-step explanation:

Restriction enzymes cut the DNA at specific restriction sites and by the mechanism of action they can form two types of ends:

• sticky ends-single-stranded overhangs are formed
• blunt ends-without overhangs.

The main advantage of sticky ends (their overhangs) is that they can complementary bind to another overhand formed by the same restriction enzyme. So, for example in cloning, if the DNA of interest and plasmid vector are cut with the same restriction enzyme, that forms sticky ends, fragment of DNA will fit into a bacterial plasmid in one direction.

On the other hand, blunt ends can be inserted into vector in both directions: head-to-tail or tail-to-head.