Question

Circular DNA molecules found in nature are

A) positively supercoiled.
B) negatively supercoiled.
C) not supercoiled, due to their small size.
D) always oriented in a triple helix to conserve space.
E) always in the Z-DNA formation.

Answer 1

In nature, circular DNA molecules are typically negatively supercoiled, which allows the DNA to be more compact and fit within the confines of the cell.

Step-by-step explanation:

Circular DNA molecules found in nature are typically negatively supercoiled. Supercoiling is a process where DNA is twisted to become more compact, and this process can result in DNA being either underwound or overwound from its normal relaxed state. In the underwound state, which is less than one turn of the helix per 10 base pairs, the DNA is said to be negatively supercoiled. Proteins and enzymes like DNA gyrase play a significant role in maintaining this supercoiled structure. This compacting is essential for fitting the genetic material within the confines of the cell, such as the DNA in E. coli, which has a genome size of 4.6 million base pairs that needs to fit into a much smaller bacterial cell.