Supercoiling is an important property of DNA tertiary structure that affects essential processes such as replication and transcription. Negative supercoiling is very important. Negative supercoiling causes unwinding of DNA and it makes the DNA strand ready for biological processes such as replication and transcription. Negative supercoiling is introduced in a DNA with the help of enzyme topoisomerase enzymes I and II. In bacteria topoisomerase enzyme II is called gyrase.