DNA Synthesis

Question 1

What is a replication origin?

Answer 1

The place where DNA replication starts

Question 2

How is a replication bubble formed?

Answer 2

DNA at the origin unwinds and allows access to the replication machinery

Question 3

How does bacterial DNA reproduce? (General overview)

Answer 3

Two replication origins that move apart as replication occurs

Question 4

How does eukaryotic DNA reproduce? (General overview)

Answer 4

Lots of replication bubbles form, and as they get bigger they join together and you end up with two new strands

Question 5

How many types of DNA polymerase are in ecoli and what are the main ones called?

Answer 5

Five types: Pole 1,2 and 3

Question 6

How many types of DNA polymerase are in eukaryotes and what are the main ones called?

Answer 6

Up to 17

Alpha, beta, gamma, delta and epsilon

Question 7

What is the alpha DNA polymerase involved in?

Answer 7

DNA replication

Question 8

What is the beta DNA polymerase involved in?

Answer 8

DNA repair

Question 9

What is the gamma DNA polymerase involved in?

Answer 9

Mitochondrial DNA replication

Question 10

What is the delta and epsilon DNA polymerase involved in?

Answer 10

Most of the cellular DNA replication

Question 11

What is a translesion DNA Polymerase?

Answer 11

When the replication fork encounters an issue (like a mutation), they are able to work around the issue and allow replication to continue

Question 12

Name the key properties of DNA polymerase

Answer 12

Acts in the 5’-3’ direction
Uses A-T G-C pairings to synthesise new strands
Has a proof reading/ editing function generally

Question 13

What are the features of a DNA primer?

Answer 13

Already on the DNA strand with a 3’OH end which can be used as a template

Question 14

How does DNA polymerase work?

Answer 14

• attracts the correct dNTP
• allows the 3’OH end to react with the INTP substrate
• the nucleotide can now be incorporated into its new position
• every time a nucleotide is added, a pyrophosphate molecule is hydrolysed into two phosphate molecules

Question 15

What enzyme facilitates the pyrophosphate -> 2x phosphate molecules reaction?

Answer 15

Pyrophosphatase

Question 16

Which of the DNA strands is replicated continuously and why?

Answer 16

The leading strand as it is travelling in the direction that the strand is opening up in (5’->3’ direction)

Question 17

What happens to the lagging strand in DNA replication

Answer 17

You have to keep initiating DNA replication, which means that the strand is made up of lots of little bits called Okazaki fragments

Question 18

How does DNA helicase work?

Answer 18

Uses ATP to break the H bonds between the base pairs in the duplex

Question 19

What does the DNA binding protein do?

Answer 19

Protects the single DNA strand from being attacked by stuff

Question 20

In bacteria, how is the primer made?

Answer 20

• primase makes an RNA copy of the DNA, which attaches to the template strand, allowing polymerase to work

Question 21

In eukaryotes how is the primer made?

Answer 21

The alpha polymerase puts down the template strand to allow the polymerase to work

Question 22

What do the repair polymerases do?

Answer 22

Remove the RNA from the lagging strands Okazaki fragments

Question 23

What does DNA ligase do?

Answer 23

Fills in the gaps left by the repair polymerases

Question 24

How does topoisomerase work?

Answer 24

Takes out the turns in the helix by taking off and reattaching the strands

Question 25

How is DNA replication so accurate?

Answer 25

Base pairing
Proof reading system
Mismatch repair system (done by enzymes)

Question 26

Why is a little bit of mutation good?

Answer 26

Roughly 1 mutation per replication allows evolution while the majority of DNA stays the same

Question 27

What happens if there is a defect in the mismatch repair genes

Answer 27

Is inherited but can mean colon cancer

Question 28

What are the antibacterial replication inhibitors called?

Answer 28

Gyrase inhibitors

Question 29

What are the antitumour replication inhibitors called?

Answer 29

Topo 2 inhibitors

Question 30

What are the antiviral replication inhibitors called?

Answer 30

Reverse transcriptase