Lecture 7

Question 1

What opens DnaB (helicase) for the DNA strand to enter?

Answer 1

Dna C binds to helicase to open the helicase ring with binding of ATP and this activated helicase encircles the 3’ end of the synthesized primer

Question 2

What happens when the helicase ring closes?

Answer 2

The hydrolysis of ATP closes the ring and Dna C dissociates, the closing of the ring around 3’ end of the primer attracts Dna Poly III to attach

Question 3

True/False: The leading and lagging polymerases are moving in concert with the helicase

Answer 3

True: Coupling requires DNA template for the lagging strand must be looped around so that both polymerases are moving in the same direction

Question 4

What happens to the lagging core every so often?

Answer 4

The lagging core disengages after each Okazaki fragment is completed, the released looped is matured (DNA poly I remove the primer and ligase seal the Fragments together).

Question 5

What happens after the loop is released from the lagging core?

Answer 5

Primase associated with the replisome initiates a new RNA primer, and the lagging core reengages with the 3’OH end of the primer and a new loop is formed and synthesis continues

Question 6

What is the role of beta clamp?

Answer 6

The beta clamp slides along the lagging and leading strand

Question 7

True/False: When the lagging strand disengages from the lagging core, the beat clamp remains on the lagging strand

Answer 7

True: Beta clamp is released from the lagging core with the Okazaki fragments

Question 8

How is the lagging strand connected to the leading strand?

Answer 8

Via the tau subunit

Question 9

What part of the DNA POLY III holds the new beta clamps?

Answer 9

The gamma complex- the gamma complex also load the new beta clamp onto newly synthesized primer

Question 10

What makes the lagging core processive again?

Answer 10

When the beta clamp with the new primer binds to the lagging core

Question 11

What structure does replicating bacterial genome make?

Answer 11

Theta

Question 12

Define catenanes and decatenanation

Answer 12

Intertwined circular Circular DNA and decatenation is the separation of the catenanes

Question 13

How are catenanes separated?

Answer 13

Through topoisomerase IV

Question 14

What is the difference in vivo and in vitro?

Answer 14

In vivo: within living organism such as cell

In vitro: laboratory setting

Question 15

What family does Topoisomerase IV belong to?

Answer 15

Topoisomerase II

Question 16

True/false: Topoisomerase II can catalyze decatenation both in vivo and in vitro?

Answer 16

False: Topoisomerase II cannot substitute Topiosomerase IV in vivo (but can decantates in vitro)