DNA Replication 1 Flashcards
What is DNA replication?
Entire genome is replicated during the cell cycle.
Are replication and cell division linked to each other?
Yes, they are not independent
What were Watson and Crick famous for discovering?
Molecular structure of nucleic acids
Why was the structure of the double helix important for the discovery of DNA replication?
- Hydrogen bonds were easier to break between double helix
- Free strands act as templates for new strand synthesis
- Understanding that DNA structure was key to howv it replicates
Daughter duplex is…
newly formed strand from parent duplex
What were the preliminary models of DNA replication that were considered?
- Semi-conservative
- Conservative
- Dispersive
Explain the semi-conservative model
DNA replication results in rach strand acting as a template for the next generation of DNA helices.
What is the conservative model?
Idea that old strand completely replicates whilst keeping its own strands.
What is the dispersive model?
Idea that each new generation of DNA strands consist of both new and old parts. No strand is entirely new or parental.
How did Meselson and Stahl go about proving the hypotheses?
Radioactive labelling of DNA to distinguish between parental and daiughter strands using heavy and light isotopes of Nitrogen.
- Heavy isotope 15N
- Light isotope 14N
What is centrifugation allow meselson and stahl to identify?
Allows to show how the generqation of new E.coli bacteria distributed the isotopes of nitrogen away from each other.
Why did the results of the experiment fit the semi-conservative model?
Incubation of heavy cells in light nitrogen medium showed the centrifugation to gradually gravitate towards lighter residues of DNA.
What is a replicon?
A nucleic acid molecule, or part of one, which replicates as a unit, beginning at a specific site within it.
Do bacteria have multiple origin points in replicons?
No they do not.
What is the significance of the replication fork?
Site of DNA helix where the parental duplex seperate into 2 strands during DNA replication.
Is replication unidirectional or bidirectional in bacteria?
Both. Termination sequences are found roughly 100kb from the midway point. This is called a replication fork trap.
