Molecular Biology (3)

Question 1

Describe the initiation of prokaryotic DNA replication

Answer 1

Initiator protein (DnaA) binds to origin of replication (oriC) 
DnaC enables binding of DnaB (helicase) to to DNA-DnaA complex - DnaB causes bidirectional DNA unwinding

Question 2

Describe the process of nick translation on the lagging strand

Answer 2

DNA polymerase I extends Okazaki fragment in 5’-3’ direction
DNA polymerase I exonuclease activity removes next RNA primer
DNA polymerase dissociates after extending by 10-12 nucleotides
DNA ligase binds to nick

Question 3

What are the components of the replisome protein complex and what are their roles?

Answer 3

Sliding clamp - holds DNA polymerase to DNA
Polymerase core
Primosome - contains DNA helicase
Primase - adds RNA primers
SSB tetramer - binds to lagging strand to prevent reannealing to form dsDNA

Question 4

How many types of DNA polymerases do prokaryotes have and what are they called?

Answer 4

5

DNA Pol I-V

Question 5

What is the structural difference between the different prokaryotic DNA polymerases?

Answer 5

Different number of subunits

Question 6

Which prokaryotic DNA polymerase has the highest processivity?

Answer 6

DNA Pol III

Question 7

What is DNA Pol III and what are its components and their roles?

Answer 7

Holoenzyme
Core complex - 2α subunits (polymerases) and ε subunit (3’-5’ exonuclease)
Sliding clamp - 2 β subunits
γ subunit - clamp-loading