Replication

Question 1

Helicase role

Answer 1

unwinding the double helix

Question 2

Primase role

Answer 2

synthesis of primers

Question 3

Single-stranded binding protein (SSB) role

Answer 3

stabilising single-stranded regions

Question 4

Topoisomerase role

Answer 4

release of topological stress

Question 5

DNA polymerase role

Answer 5

DNA synthesis

Question 6

5’-3’ exonuclease role

Answer 6

primer removal

Question 7

Ligase role

Answer 7

joining of okazaki fragments

Question 8

Four steps of initiation

Answer 8

1. recognition of replication origin
2. partial unwinding of DNA helix
3. Helicase entry, strand separation
4. primer synthesis

Question 9

E.coli replication origin (name, no. of bps, repetitive sequences)

Answer 9

-OriC
-240 bp
-9 mer x4 (DNAa binding site)
13 mer x3 (DNAb binding site)

Question 10

3 things that make DNA synthesis in eukaryotes more complicated than in prokaryotes

Answer 10

1. Much bigger genome (e.g. E.coli: 4mil bp Human: 6bil bp)
2. More chromosomes (e.g. E. coli: 1 Humans: 23)
3. Linear chromosomes

Question 11

Processicivity

Answer 11

capacity of an enzyme to stay bound to its substrate

Question 12

DNApol I enzyme activities

Answer 12

1. polymerisation
2. 3’ - 5’ exonuclease activity
3. 5’ - 3’ exonuclease activity

Question 13

DNApol II enzyme activities

Answer 13

1. polymerisation

2. 3’ - 5’ exonuclease activity

Question 14

DNApol III enzyme activities

Answer 14

1. polymerisation

2. 3’ - 5’ exonuclease activity

Question 15

E. coli polymerase III properties

Answer 15

1. > 600 kD, 10 polymers

2. 750 nucleotides per sec

Question 16

E. coli polymerase III functional components

Answer 16

1. core polymerase
2. sliding clamp
3. clamp loader
4. tau subunit

Question 17

Polymerase switching

Answer 17

after the polα/primase complex synthesises a 10nt primer and extends it 15nt, Replication Factor C displaces it and loads PCNA onto the template allowing pol 𝛿 to continue extending the primer