Question

Ligation reactions occur most efficiently between DNA fragments:

A. that have sticky ends.

B.   that have blunt ends.

C. that have complementary sticky ends.

D. that are cleaved with different restriction enzymes.

E. where one fragment has a sticky end and the other has a blunt end.

Answer 1

Ligation reactions occur most efficiently between DNA fragments that have complementary sticky ends.

Explanation -

• Blunt ends are also known as the non-cohesive restriction enzymes and they terminate in a base pair therefore it cannot be the right answer.
• Sticky ends are the sequences from asymmetrical cleavage from the restriction enzymes at one end. the cleavage produces the two ends of DNA without any complementary bases. Therefore, ligation can occur but not as most efficiently as with complementary sticky ends.
• DNA fragments that are cleaved with different restriction enzymes will not ligate.
• DNA fragments where one fragment has a sticky end and the other has a blunt end will also not ligate due to difference in the complementary base pairing.