LIFE SCIENCE

Detailed explanation-1: -Like topoisomerase I, topoisomerase II catalyzes relaxation of supercoiled DNA. However, topoisomerase II is unique in its ability to catalyze the decatenation of intact double-stranded DNA, a property that allows the enzyme to separate replicated DNA molecules at mitosis (Nitiss, 2009a; Wang, 2002).

Detailed explanation-2: -In eukaryotes, IIA enzymes catalyze the relaxation of positively or negatively supercoiled DNA, as well as the decatenation and unknotting of DNA helices. Bacterial IIA topoisomerases, including DNA gyrase and topoisomerase IV (TopIV), can also decatenate and unknot DNA, but they also possess unique activities.

Detailed explanation-3: -DNA topoisomerases are enzymes that catalyze DNA structural alterations that include relaxation of positively and negatively supercoiled DNA and resolution of DNA knots and catenanes. These enzymes create transient DNA breaks to catalyze these changes in DNA topology.

Detailed explanation-4: -DNA gyrase introduces supercoils, and DNA topoisomerase I prevents supercoiling from reaching unacceptably high levels.

Detailed explanation-5: -Type II topoisomerases are involved in both decatenation of daughter chromosomes, and relieving the positive supercoiling ahead of the replication fork.