DNA Replication

Question 1

What direction is DNA replicated in?

Answer 1

5’ - 3’

Question 2

Name as many DNA replication enzymes as you can!

there are 7

Answer 2

Topoisomerase
DNA Helicase
DNA Polymerase
DNA Primase
DNA Ligase
Ribonuclease
Repair DNA Polymerase

Question 3

How is DNA Unravelled?

Answer 3

By Topoisomerase

Question 4

Which enzyme seperates the DNA strand?

Answer 4

DNA Helicase

Question 5

What does DNA Helicase require?

Answer 5

ATP to break Hydrogen Bonds

Question 6

What does DNA Polymerase do?

Answer 6

Adds nucleotides to the 3’ end of a nucleotide chain

Question 7

What does DNA Polymerase require for DNA Synthesis?

Answer 7

A Template strand
Oligonucleotide primer
DNA Primase
Deoxynucleotide triphosphates (dNTPs)

Question 8

What is DNA replication described as?

Answer 8

Semi-conservative; each new strand consists of a template strand from the parental DNA and a newly synthesised strand

Question 9

What is an Oligonucleotide primer?

Answer 9

A short strand of RNA made by DNA primase added at the beginning of synthesis and removed later.

Question 10

What are dNTPs?

Answer 10

Deoxynucleotide triphosphates - Nucleotides with 3 phosphates attached

Question 11

Where does replication of DNA begin?

Answer 11

The origin of replication, creating a replication fork

Question 12

Describe the two strands of DNA during replication

Answer 12

Leading strand: Can be continuously synthesised

Lagging strand: Cannot be continuously synthesised as the 3’ end is facing away from the fork

Question 13

Describe how the leading strand is synthesised

Answer 13

Continuously by DNA polymerase adding dNTPs to the 3’ end

Question 14

Why are dNTPs used in synthesis?

Answer 14

Hydrolysis of the triphosphate group releases energy used to add more nucleotides

Question 15

What is the synthesis of the lagging strand split up into?

Answer 15

Okazaki fragments

Question 16

Describe the synthesis of Okazaki fragments

Answer 16

DNA Primase adds the Oligonucleotide primer to the template strand.
DNA Polymerase adds dNTPs at the 3’ end of the primer until the previous fragment is reached.

Question 17

Describe the joining of Okazaki fragments

Answer 17

Ribonuclease removes the RNA primer
Repair DNA polymerase replaces the RNA with DNA
DNA ligase joins two Okazaki fragments together.

Question 18

What ensures the DNA polymerase is in the right place?

Answer 18

The sliding clamp

Question 19

What may happen during the synthesis of the lagging strand, and how is this prevented?

Answer 19

Local folding.

Addition of Single strand DNA binding protein.

Question 20

Describe the proofreading mechanism in DNA synthesis

Answer 20

DNA polymerase checks the previous nucleotide is correct before adding the next.