DNA replication Flashcards
What type of replication does DNA Undergo?
Semi-conservative replication
Who discovered semi-conservative replication?
Meselson and Stahl
How did Meselson and Stahl prove semi-conservative replication? (3)
- Grow bacteria in heavy N15
- Grow bacteria in light N14 - hybrid N15/N14 produced
- Continue to grow bacteria in N14 - centrifuge, light and hybrid produced
Describe the end structures of a DNA strand:
5’ phosphate end and 3’ hydroxyl (OH) end
Which end can a DNA strand be extended from?
3’ end on the OH
What are the 3 things DNA needs for replication?
- dNTP’s (deoxyribonucleotide triphosphate)
- A template strand
- A primer
Is DNA replication a continuous or discontinuous process?
DNA replication is semi-discontinuous as the leading 3’ strand synthesises continuously and the lagging 5’ strand is discontinuous
Which enzyme unwinds and unzips the DNA molecule?
DNA helicase
Which enzyme synthesises base pairing?
DNA polymerase
How is DNA replication primed? (2)
RNA - synthesised by primase
Interrupts DNA sequence (Okazaki fragments)
How is RNA removed from the chain to end the synthesis?
5’-3’ exonuclease removes it
How are the Okazaki fragments (nicks) sealed?
DNA ligase seals them in a condensation reaction
Is DNA replication bidirectional or unidirectional?
It can be both, bidirectional is twice as fast but more complicated but more common
How does bidirectional DNA replication work?
It produces 2 forks that are visible in an experiment using tritium isotopes which can be detected