DNA replication Flashcards

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1
Q

What type of replication does DNA Undergo?

A

Semi-conservative replication

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2
Q

Who discovered semi-conservative replication?

A

Meselson and Stahl

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3
Q

How did Meselson and Stahl prove semi-conservative replication? (3)

A
  1. Grow bacteria in heavy N15
  2. Grow bacteria in light N14 - hybrid N15/N14 produced
  3. Continue to grow bacteria in N14 - centrifuge, light and hybrid produced
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4
Q

Describe the end structures of a DNA strand:

A

5’ phosphate end and 3’ hydroxyl (OH) end

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5
Q

Which end can a DNA strand be extended from?

A

3’ end on the OH

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6
Q

What are the 3 things DNA needs for replication?

A
  1. dNTP’s (deoxyribonucleotide triphosphate)
  2. A template strand
  3. A primer
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7
Q

Is DNA replication a continuous or discontinuous process?

A

DNA replication is semi-discontinuous as the leading 3’ strand synthesises continuously and the lagging 5’ strand is discontinuous

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8
Q

Which enzyme unwinds and unzips the DNA molecule?

A

DNA helicase

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9
Q

Which enzyme synthesises base pairing?

A

DNA polymerase

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10
Q

How is DNA replication primed? (2)

A

RNA - synthesised by primase

Interrupts DNA sequence (Okazaki fragments)

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11
Q

How is RNA removed from the chain to end the synthesis?

A

5’-3’ exonuclease removes it

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12
Q

How are the Okazaki fragments (nicks) sealed?

A

DNA ligase seals them in a condensation reaction

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13
Q

Is DNA replication bidirectional or unidirectional?

A

It can be both, bidirectional is twice as fast but more complicated but more common

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14
Q

How does bidirectional DNA replication work?

A

It produces 2 forks that are visible in an experiment using tritium isotopes which can be detected

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