DNA Replication

Question 1

What are the steps of Prokaryotic DNA Replication?

Answer 1

Complementary Strand Separation
Replication Fork Formation
Chain Elongation
RNA Primer Excision and Replacement by DNA
Proofreading of newly synthesized DNA
Termination

Question 2

Prokaryotic DNA Replication: Complementary Strand Separation
What does DNA Polymerase use as a template?

Answer 2

ssDNA

Question 3

Prokaryotic DNA Replication: Complementary Strand Separation
Ori C (origin of replication) is consensus ____ which facilitates ____

Answer 3

__A-T rich__
__melting__

A-T rich means that the hydrogen bonds are weaker which facilitates separation

Question 4

Prokaryotic DNA Replication: Complementary Strand Separation
How many points of origin of replication in prokaryotes?

Answer 4

Single origin

Question 5

Prokaryotic DNA Replication: Complementary Strand Separation
What are the proteins required for Initiation and Strand Separation?

Answer 5

DnaA
DNA helicase DnaB
Single-Stranded Binding Protein

Question 6

Prokaryotic DNA Replication: Complementary Strand Separation
Function of DnaA

Answer 6

Binds to OriC sequences
Helps DNA melting and strand separation

Question 7

Prokaryotic DNA Replication: Complementary Strand Separation
Function of DnaB

Answer 7

Binds to ssDNA and unwinds the double helix

Question 8

Prokaryotic DNA Replication: Complementary Strand Separation
Single-Stranded Binding Protein

Answer 8

Binds to ssDNA to prevent reannealing

Question 9

Prokaryotic DNA Replication: Complementary Strand Separation
Why may supercoils form during complementary strand separation?

Answer 9

Due to double helix separation

Question 10

Prokaryotic DNA Replication: Complementary Strand Separation
Which enzymes help release supercoils?

Answer 10

DNA Topoisomerase I
DNA Topoisomerase II

Question 11

Prokaryotic DNA Replication: Complementary Strand Separation
Steps of DNA Topoisomerase I action

Answer 11

Cuts one DNA strand allowing the other strand to pass through and relieve supercoil tension
Reseals cut after completion

Question 12

Prokaryotic DNA Replication: Complementary Strand Separation
DNA Topoisomerase I ATP requirement

Answer 12

No ATP requirement

Question 13

Prokaryotic DNA Replication: Complementary Strand Separation
Steps of DNA Topoisomerase II action

Answer 13

Binds tightly to DNA double helix
Makes transient breaks in both strands
Enzyme causes a second stretch of DNA double helix to pass through the break
Reseals break

Question 14

Prokaryotic DNA Replication: Complementary Strand Separation
DNA Topoisomerase II ATP requirement

Answer 14

ATP required

Question 15

Prokaryotic DNA Replication: Complementary Strand Separation
Which drugs may target topoisomerases?

Answer 15

Anticancer Agents (Chemotherapeutics)

Question 16

Prokaryotic DNA Replication: Replication Fork Formation
The 2 strands unwind in opposite directions forming a …

Answer 16

replication bubble

Question 17

Prokaryotic DNA Replication: Replication Fork Formation
Direction of DNA Polymerase reading

Answer 17

3’ → 5’

Question 18

Prokaryotic DNA Replication: Replication Fork Formation
In what direction does DNA Polymerase synthesize new DNA?

Answer 18

5’ → 3’

Question 19

Prokaryotic DNA Replication: Replication Fork Formation
Which strand is synthesized continuously

Answer 19

Leading Strand (3’ → 5’) towards replication fork

Question 20

Prokaryotic DNA Replication: Replication Fork Formation
Which strand is synthesized non-continuously?

Answer 20

Lagging Strand (5’ → 3’) away from replication fork

Question 21

Prokaryotic DNA Replication: Replication Fork Formation
How is the Lagging Strand synthesized?

Answer 21

Short fragments called Okazaki fragments interupted by RNA primers

Question 22

Prokaryotic DNA Replication: Replication Fork Formation
How are Okazaki fragments linked?

Answer 22

After removing RNA primers, fragments are joined by ligase

Question 23

Prokaryotic DNA Replication: Replication Fork Formation
What initiates DNA strand synthesis?

Answer 23

RNA Polymerase adds RNA primers for DNA polymerase to act on

Primers are removed after replication

Question 24

Prokaryotic DNA Replication: Chain Elongation
Describe the process of chain elongation

Answer 24

DNA polymerase elongates DNA by adding dNTPs from the RNA primer

Question 25

**Prokaryotic DNA Replication: Chain Elongation** DNA polymerase III function

Answer 25

Chain elongation of leading and lagging strands

Question 26

**Prokaryotic DNA Replication: Chain Elongation** How many dNTPs (nucleotides) must be presents for elongation process?

Answer 26

4

Question 27

**Prokaryotic DNA Replication: RNA Primer Excision and Replacement by DNA** How far does the DNA polymerase III go on the lagging strand?

Answer 27

Until it is blocked by proximity to RNA primer

Question 28

**Prokaryotic DNA Replication: RNA Primer Excision and Replacement by DNA** What catalyses the replacement of the RNA primer?

Answer 28

DNA Polymerase I

Question 29

**Prokaryotic DNA Replication: RNA Primer Excision and Replacement by DNA** What catalyses the formation of the phosphodiester bonds between Okazaki Fragments?

Answer 29

DNA Ligase

Question 30

**Prokaryotic DNA Replication: Proofreading of Newly Synthesized DNA** Describe the process of proofreading DNA

Answer 30

DNA Polymerase has exonuclease activity in 3' → 5' direction

Question 31

**Prokaryotic DNA Replication: Termination** How is DNA replication terminated?

Answer 31

Binding of specific protein to replication termination sites of DNA

Question 32

Where does eukaryotic DNA replication originate from?

Answer 32

Multiple sites along DNA helix

Question 33

What is the benefit of having multiple origins of replication?

Answer 33

Faster replication process

Question 34

**DNA Replication in Eukaryotes** How are RNA primers removed in Eukaryotes?

Answer 34

RNAase H

Question 35

**DNA Replication in Eukaryotes** What are the eukaryotic DNA polymerases?

Answer 35

Pol α Pol ε Pol δ Pol β Pol γ

Question 36

**DNA Replication in Eukaryotes** Pol α function

Answer 36

Synthesizes short RNA segment Extended by Pol α 5' → 3' polymerase activity

Question 37

**DNA Replication in Eukaryotes** Pol ε function

Answer 37

Completes DNA synthesis on leading strand

Question 38

**DNA Replication in Eukaryotes** Pol δ function

Answer 38

Elongates Okazaki Fragments of lagging strand Use 3'→5' exonuclease activity to proofread newly synthesized DNA

Question 39

**DNA Replication in Eukaryotes** Pol β function

Answer 39

Involved in gap filling in DNA repair

Question 40

**DNA Replication in Eukaryotes** Pol γ function

Answer 40

Replicates mitochondrial DNA

Question 41

**DNA Replication in Eukaryotes** Which proteins control progression through cell cycle?

Answer 41

Cyclins Cyclin-Dependent Kinases (CDKs)

Question 42

**DNA Replication in Eukaryotes** What is an oncogene?

Answer 42

Altered gene which accelerates cell division E.g. Ras and MYC oncogenes

Question 43

**DNA Replication in Eukaryotes** What are tumor suppressor genes?

Answer 43

Inhibit cell growth and division E.g. P53 gene and RB gene