Question

With the addition of linking number (Lk) by +2 to a relaxed DNA consisting of Lk = 200, which of the following occurs?

• A. DNA undergo positive supercoiling with the Lk 202
• B. DNA undergo positive supercoiling with the Lk 198
• C. DNA undergo negative supercoiling with the Lk 202
• D. Structure does not change

Hint:

Understand the relationship between linking number, supercoiling, and DNA topology.

Answer 1

The Correct Option is A

The linking number (Lk) represents the total twists and writhes of a DNA molecule. Adding +2 to the linking number of relaxed DNA changes the topology and introduces positive supercoiling. The new linking number is Lk = 202, which leads to torsional stress and a more tightly coiled DNA.