Origin Of replication

Question 1

What is the typical shape of prokaryote genomes?

Answer 1

Circular

Question 2

How many origins of replication (ORI) do prokaryote genomes usually contain?

Answer 2

One

Question 3

What is the function of the ORI in DNA replication?

Answer 3

It is the site where DNA replication is initiated

Question 4

In E. coli, how is the replication process regulated?

Answer 4

Only at the point of initiation

Question 5

What happens once the replication fork is established in E. coli?

Answer 5

Replication proceeds until completion

Question 6

What are the products of DNA replication in prokaryotes?

Answer 6

Two circular daughter DNA molecules

Question 7

Fill in the blank: DNA replication is initiated at distinct sites called _______.

Answer 7

origins of replication (ORI)

Question 8

What is OriC?

Answer 8

OriC is the origin of replication in E. coli, with a length of 245 bp.

Question 9

What are the important sequences found in OriC?

Answer 9

OriC contains two important sequences: 13-nucleotide sequences and 9-nucleotide sequences.

Question 10

How many 13-nucleotide sequences are present in OriC?

Answer 10

There are three 13-nucleotide sequences in tandem array.

Question 11

How many 9-nucleotide sequences are present in OriC?

Answer 11

There are four 9-nucleotide sequences present.

Question 12

What is the significance of the 9-nucleotide sequences in OriC?

Answer 12

The 9-nucleotide sequences serve as binding sites for DnaA protein.

Question 13

What is the consensus sequence of the tandem array of 13-mer sequences?

Answer 13

The consensus sequence is GATCTNTTNTTTT.

Question 14

What is the characteristic of the 13-mer tandem sequences at the Ori?

Answer 14

They are A-T rich.

Bonding between A-T is weaker than G-C, facilitating easier melting and strand separation of the DNA molecule at this region.

Question 15

What initiates the process of replication at the Ori?

Answer 15

DnaA initiator proteins bind to the 9-nucleotide regions.

Question 16

What is the consensus sequence for the binding sites of DnaA protein?

Answer 16

GATCTNTTNTTTT.

Question 17

What is the length of the oriC region?

Answer 17

245 bp.

Question 18

What are the 9-mers in E.coli OriC?

Answer 18

The 9-mers are specific DNA sequences at the origin of replication where initiator proteins bind.

Question 19

What role does DnaA play in the initiation of replication?

Answer 19

DnaA is an initiator protein that binds to the 9-mers at the origin.

Question 20

What is the function of DnaC?

Answer 20

DnaC is a helicase inhibitor protein that delivers helicase (DnaB) to the template.

Question 21

What is the role of ATP in the initiation of replication?

Answer 21

ATP is required for the binding of DnaA and the formation of the initial complex.

Question 22

What is DnaB?

Answer 22

DnaB is a helicase that unwinds the DNA during replication.

Question 23

What occurs at the 13-mer sequences during replication initiation?

Answer 23

Strand separation occurs at the region of the 13-mer sequences.

Question 24

What is the prepriming complex?

Answer 24

The prepriming complex is formed when DnaB clamps around each single strand of DNA.

Question 25

How does helicase unwind the DNA?

Answer 25

Helicase unwinds the DNA in opposite directions away from the origin.

Question 26

What is the role of initiator proteins (DnaA protein) in DNA replication?

Answer 26

Initiator proteins bind to the origin of replication and break hydrogen bonds between bases.

Question 27

What is the function of helicase inhibitor (DnaC)?

Answer 27

DnaC delivers helicase to the DNA template.

Question 28

What does DNA helicase (DnaB) do during replication?

Answer 28

DnaB opens the helix and binds primase to form the primosome protein complex.

Question 29

What is the role of single stranded binding protein (ssb)?

Answer 29

ssb binds to single stranded DNA in the replication bubble and prevents it from re-annealing or forming secondary structure.

Question 30

What is the primosome?

Answer 30

The primosome is a protein complex formed by helicase and primase.

Question 31

What does 'oric' refer to in DNA replication?

Answer 31

Oric refers to the origin of replication in prokaryotes.

Question 32

What components are involved in the pre-primosome complex?

Answer 32

The pre-primosome complex includes DnaA, DnaB, and primase.

Question 33

Describe the difference between a leading dna strand and a lagging dna strand.

Answer 33

Leading : continuous in the direction of the replication fork Lagging: discontinuous in the opposite direction of the fork

Question 34

Why are Okazaki fragments, formed?

Answer 34

They are synthesized from the discontinuous lagging strand. DNA polymerase must elongate from 5' to 3' direction. It needs enough 3' to be exposed to do so. Okazaki fragments continue to help the elongation of 3' end , then they are lysed together(Ligase)