Which of the Following Types of DNA are Often Supercoiled

Question

Which of the following types of DNA are often supercoiled?
A)extremely long linear DNA,such as seen in human chromosomes
B)very short linear DNA
C)circular DNA
D)DNA molecules that contain both circular and linear regions
E)all of the above

Accepted Answer

Circular DNA is often supercoiled, as the circular shape creates tension and twisting that leads to supercoiling. Linear DNA can also become supercoiled under certain conditions, but it is not as common. Very short linear DNA may not have enough length to become supercoiled, and extremely long linear DNA such as human chromosomes may instead form structural loops called chromatin. DNA molecules that contain both circular and linear regions may have supercoiling in the circular portion but not in the linear portion. Therefore, only choice C, circular DNA, is often supercoiled.