Which type of supercoiling is most common in DNA?

Negative supercoiling is the most common type found in DNA. This type of supercoiling occurs when the DNA helix is twisted in the opposite direction to the right-handed spiral of the double helix, introducing underwinding. The significance of negative supercoiling lies in its role in promoting processes such as DNA replication and transcription. Negative supercoiling makes it easier for the double helix to separate, thereby increasing access to the genetic information necessary for these processes.

In contrast, positive supercoiling, which is winding of the helix in the direction of the helix, is less common in the context of the cell's normal physiological state. While it can occur during rigorous processes like transcription, DNA repair, or as a consequence of DNA supercoiling during replication, it generally does not dominate in living organisms. Overall, the prevalence of negative supercoiling is a crucial aspect of DNA dynamics and cellular function, making it the predominant type encountered in genomic DNA.