Lecture 16: DNA Replication Flashcards
1
Q
How does prokaryotic replication occur?
A
- DNA is “unzipped” from both directions
- From 5 prime to 3 prime direction
- 2 parent template strands created
2
Q
What is RNA polymerase (primase)(prune)?
A
- An enzyme that makes small RNA primers (starting point for DNA polymerisation)
3
Q
What is helicase? (Honeydew Melon)
A
- Recognises AT rich origin of replication
- Separates two DNA strands from each other
- Strand replication occurs in 5’ - 3’ direction easily, remember anti parallel, make little strands
4
Q
Replication is semidiscontinuous. What are the two strands called?
A
- Leading + Lagging Strand
5
Q
What is topoisomerase? (Tomato)
A
- Releases tension (cut DNA)
6
Q
What do single stranded binding proteins do?
A
- Protect DNA strand regions from being attacked and destroyed
- Prevent two single strand molecules from snapping back together
7
Q
What is DNA polymerase III? (Potato)
A
- They will use 3’ hydroxyl group (from RNA) to add nucleotides to the template (leading strand)
8
Q
How does the synthesis of the lagging strand occur?
A
- Short little fragments made in 5’ –> 3’ direction
- Primase (RNA template), DNA Polymerase adds nucleotides
- Bits are not linked together until DNA pol I appears
9
Q
What does DNA Polymerase I do?
A
- Has the ability to recognise DNA + RNA hybrids and takeaway RNA
- Will use hydroxyl group and start extending to fill in gap
10
Q
What is the function of Ligase? (Lettuce)
A
- Creates phosphodiester bond between Phosphate + Hydroxyl bits
- New DNA strand is now completely synthesised
11
Q
What can an exonuclease do?
A
- Chop away from 5’ to 3’ or 3’ to 5’ (at the ends)
12
Q
What can an endonuclease do?
A
- Chop away the middle bit of a strand
13
Q
What happens when an incorrect base is inserted during replication?
A
- DNA Pol III has proofreading mechanism of original strand
- Synthesises a new base
- Exonuclease
14
Q
What happens when an incorrect base is inserted after replication?
A
- Goes into the middle, removes incorrect and a few other bases on either side
- DNA Pol Synthesises new bases
15
Q
What happens if you don’t correct DNA?
A
- If not corrected, DNA error becomes permanent (mutation)
