Difference Between Topoisomerase I and II

Type I topoisomerases relax DNA (i.e., remove supercoils) by nicking and closing one strand of duplex DNA (see Figure 12-14). Type II topoisomerases change DNA topology by breaking and rejoining double-stranded DNA. ... Both replicated circular and linear DNA chromosomes are separated by type II topoisomerases.

1. What is the difference between topoisomerase 1 and 2?
2. What is the function of topoisomerase 1?
3. What do the enzymes topoisomerase I and topoisomerase II have in common?
4. How many types of topoisomerases are there?
5. What is the function of topoisomerase II?
6. What does Supercoiling mean?
7. What are the types of topoisomerase?
8. What enzyme prevents Supercoiling?
9. What is positive and negative supercoiling?
10. What does gyrase do?

What is the difference between topoisomerase 1 and 2?

Topoisomerase I refers to the enzymes which cut one of the two strands of double-stranded DNA, relax the strand, and reanneal the strand while topoisomerase II refers to the enzymes which cut both strands of the DNA helix simultaneously in order to manage DNA tangles and supercoils.

What is the function of topoisomerase 1?

Topoisomerase I is a ubiquitous enzyme whose function in vivo is to relieve the torsional strain in DNA, specifically to remove positive supercoils generated in front of the replication fork and to relieve negative supercoils occurring downstream of RNA polymerase during transcription.

What do the enzymes topoisomerase I and topoisomerase II have in common?

What do the enzymes topoisomerase I and topoisomerase II have in common? They both have nuclease activity. They both create double-strand DNA breaks. ... They both can create winding (tension) in an initially relaxed DNA molecule.

How many types of topoisomerases are there?

Classes. DNA topoisomerases are divided into two classes: type I enzymes (EC; topoisomerases I, III and V) break single-strand DNA, and type II enzymes (EC; topoisomerases II, IV and VI) break double-strand DNA.

What is the function of topoisomerase II?

Type II topoisomerases change DNA topology by breaking and rejoining double-stranded DNA. These enzymes can introduce or remove supercoils and can separate two DNA duplexes that are intertwined (see Figure 12-16).

What does Supercoiling mean?

Supercoils refer to the DNA structure in which double-stranded circular DNA twists around each other. This is termed supercoiling, supertwisting or superhelicity -- meaning the coiling of a coil, also understood in terms of knots.

What are the types of topoisomerase?

Topoisomerases (or DNA topoisomerases) are enzymes that participate in the overwinding or underwinding of DNA. ... The winding problem of DNA arises due to the intertwined nature of its double-helical structure. During DNA replication and transcription, DNA becomes overwound ahead of a replication fork.

What enzyme prevents Supercoiling?

DNA gyrase introduces supercoils, and DNA topoisomerase I prevents supercoiling from reaching unacceptably high levels.

What is positive and negative supercoiling?

Positive supercoiling of DNA occurs when the right-handed, double-helical conformation of DNA is twisted even tighter (twisted in a right-handed fashion) until the helix begins to distort and "knot." Negative supercoiling, on the other hand, involves twisting against the helical conformation (twisting in a left-handed ...

What does gyrase do?

DNA gyrase is an essential bacterial enzyme that catalyzes the ATP-dependent negative super-coiling of double-stranded closed-circular DNA. Gyrase belongs to a class of enzymes known as topoisomerases that are involved in the control of topological transitions of DNA.