Chapter 6 Part 1 Flashcards
Which DNA replication hypothesis was correct?
Semiconservative model where there is one strand of parent DNA and one strand of the daughter (new) DNA for each double helix
Explain the dispersive hypothesis
where each strand of DNA has a mixture of the daughter and parental DNA (some new/ some old)
Explain the conservative hypothesis
this is where there is a parent double helix and a daughter double helix (all new and all old)
who ran the experiment to determine how DNA is passed down
Meselson and Stahl
What two isotopes were used in the Meselson- Stahl experiment?
14N (light) and 15N (heavy)
Explain how the conservative hypothesis was ruled out
Bacteria grown in 15N were transferred into 14N for one round of 14N, this bacteria was then centrifuged, and the band shown was between the 14N and 15N control. If it were conservative we would have had two bands.
How was the dispersive hypothesis ruled out?
The sample from the conservative test was heated, and the single band then split into two seprate bands. If it was dispersive the band wouldn’t split.
What does Helicase do?
It unwinds the DNA duplex using ATP
what does SSB do?
Binds unwound region and it prevents re-annealing
What does DNA Polymerase do?
Polymerizes new strand and error checks
What does the sliding clamp do?
It increases processivity of DNA polymerase
What does the clamp loader do?
Helps the sliding clamp assemble
What does primase do?
it lays down RNA primer
What does nuclease do?
it removes RNA primer
what does DNA repair polymerase do?
it fills in gaps left by RNA primers
What does DNA ligase do?
it joins Okazaki fragments
What does DNA topoisomerase do?
It relieves torsional stress.
Replication origins are?
A-T rich
How is a template strand oriented?
From 3’ - 5’
How is the new strand formed?
from 5’ - 3’
Which strand is the leading strand?
The strand that is synthesized continuously (doesn’t require another primer to continue)
How do replication forks move?
Bidirectionally (opposite ways)
What is the Lagging strand?
It is synthesized in small okazaki fragments (requires another primer to continue synthesizing)
Where are telomers located?
At the end of chromosomes
How does telomerase solve the End replication problem?
Telomerase binds with the template strand and adds additional coding, then DNA polymerase completes the lagging strand with the proper coding according to the template strand
What would happen if DNA Ligase went missing?
the DNA strand would no longer be continuous
What would happen if the sliding clamp went missing?
DNA polymerase would not be able to synthesize new DNA
What would happen if nuclease went missing?
We would have RNA and DNA all in one strand
What would happen if DNA Helicase went missing?
Replication would not be able to begin
