DNA Replication_Lec3

Question 1

DNA Replication

Answer 1

semi-conservative
discontinues
bi-directional
5 -> 3

Question 2

Consequences of Replication

Answer 2

1. Beginning of replication commits cell division
2. Division cannot take place before completion of replication
3. When replication has started the process must be completed
   - interrupted = successful progeny will not form

Question 3

Replicon

Answer 3

The part of the genome where replication takes place

- contains an origin of replication

Question 4

Origin

Answer 4

specific point(s) on a genome where replication begins

Question 5

Replication Fork

Answer 5

Area in replicon where the two strands of the DNA duplex are separated and where DNA synthesis takes place

Question 6

Replication in E. coli

• origin
• Termination
• After Termination

Answer 6

origin of replication - oriC

Termination

• terC1 and terC2 (jointly terC)
• tus gene protein binds to terC = terminate process

After Termination

• DNA dimer resolved by site-specific recombination at dif site
• with the aid of XerC and XerD Recombinases

Question 7

Prokaryote vs Eukaryote

Answer 7

Prokaryote

• bi-directional
• single origin on genome

Eukaryote

• bi-directional
• various origins on each chromosome
  * Each fires only once per replication

Question 8

Ensure only one genome per cell

Answer 8

Genome Segregation

• Genomic DNA undergoes methylation on A of GATC sequence = dam methylation
• After dam methylation has taken place partially = oriC binds once to cell membrane during replication

Question 9

E. coli divides faster than once every 60 min

Answer 9

Replication begin before previous cell division has been completed (NOT ALLOWED), HOW DO THEY MANAGE THIS ANOMALY:

• Allow multiple replication forks
• Start of cell division determined by cell mass/volume - signal if replication should begin
• mass of individual cells of rapidly growing bacteria is higher