DNA Synthesis Flashcards
What is a replication origin?
The place where DNA replication starts
How is a replication bubble formed?
DNA at the origin unwinds and allows access to the replication machinery
How does bacterial DNA reproduce? (General overview)
Two replication origins that move apart as replication occurs
How does eukaryotic DNA reproduce? (General overview)
Lots of replication bubbles form, and as they get bigger they join together and you end up with two new strands
How many types of DNA polymerase are in ecoli and what are the main ones called?
Five types: Pole 1,2 and 3
How many types of DNA polymerase are in eukaryotes and what are the main ones called?
Up to 17
Alpha, beta, gamma, delta and epsilon
What is the alpha DNA polymerase involved in?
DNA replication
What is the beta DNA polymerase involved in?
DNA repair
What is the gamma DNA polymerase involved in?
Mitochondrial DNA replication
What is the delta and epsilon DNA polymerase involved in?
Most of the cellular DNA replication
What is a translesion DNA Polymerase?
When the replication fork encounters an issue (like a mutation), they are able to work around the issue and allow replication to continue
Name the key properties of DNA polymerase
Acts in the 5’-3’ direction
Uses A-T G-C pairings to synthesise new strands
Has a proof reading/ editing function generally
What are the features of a DNA primer?
Already on the DNA strand with a 3’OH end which can be used as a template
How does DNA polymerase work?
- attracts the correct dNTP
- allows the 3’OH end to react with the INTP substrate
- the nucleotide can now be incorporated into its new position
- every time a nucleotide is added, a pyrophosphate molecule is hydrolysed into two phosphate molecules
What enzyme facilitates the pyrophosphate -> 2x phosphate molecules reaction?
Pyrophosphatase
Which of the DNA strands is replicated continuously and why?
The leading strand as it is travelling in the direction that the strand is opening up in (5’->3’ direction)
What happens to the lagging strand in DNA replication
You have to keep initiating DNA replication, which means that the strand is made up of lots of little bits called Okazaki fragments
How does DNA helicase work?
Uses ATP to break the H bonds between the base pairs in the duplex
What does the DNA binding protein do?
Protects the single DNA strand from being attacked by stuff
In bacteria, how is the primer made?
- primase makes an RNA copy of the DNA, which attaches to the template strand, allowing polymerase to work
In eukaryotes how is the primer made?
The alpha polymerase puts down the template strand to allow the polymerase to work
What do the repair polymerases do?
Remove the RNA from the lagging strands Okazaki fragments
What does DNA ligase do?
Fills in the gaps left by the repair polymerases
How does topoisomerase work?
Takes out the turns in the helix by taking off and reattaching the strands
How is DNA replication so accurate?
Base pairing
Proof reading system
Mismatch repair system (done by enzymes)
Why is a little bit of mutation good?
Roughly 1 mutation per replication allows evolution while the majority of DNA stays the same
What happens if there is a defect in the mismatch repair genes
Is inherited but can mean colon cancer
What are the antibacterial replication inhibitors called?
Gyrase inhibitors
What are the antitumour replication inhibitors called?
Topo 2 inhibitors
What are the antiviral replication inhibitors called?
Reverse transcriptase
