Session 4-Cell Cycle

Question 1

Which enzyme catalyses DNA replication?

Answer 1

DNA polymerase

Question 2

How is DNA replication driven?

Answer 2

Pyrophosphate hydrolysis

Question 3

What are the three stages of DNA replication?

Answer 3

Initiation
Elongation
Termination

Question 4

What happens during initiation?

Answer 4

The origin of replication is recognised
DNA polymerase is recruited
Primase helps to kick-start reaction

Question 5

What does DNA helicase do?

Answer 5

Unwinds the double helix

Question 6

DNA polymerase extends 3’ ends only-what does this lead to? (3)

Answer 6

Leading strand (continuous) 
Lagging strand (discontinuous) 
Okazaki fragments

Question 7

Which enzyme joins fragments?

Answer 7

DNA ligase

Question 8

What happens in termination?

Answer 8

Two facing replication forks meet and DNA ligase joins the final fragments

Question 9

Why are telomeres needed?

Answer 9

So the primer can prime to it and prevent the shortening of DNA (telomeres are non-coding DNA)

Question 10

How might interfering with telomeres allow the treatment of cancer?

Answer 10

If you can speed up the process of telomere shortening, the cell will eventually senesce and you can then stop cancer cells replicating