1.5 DNA replication Flashcards

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1
Q

name the 2 hypotheses:

A
  • semi-conservative replication
  • conservative replication
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2
Q

what does the semi-conservative hypothesis propose

A
  • 2 nucleotide chains separate like a zip,
    ∴ acting as templates for formation of further chains.
  • no daughter will me made of exactly the same bases as original molecule
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3
Q

what does conservative hypothesis propose

A
  • a new DNA molecule will form alongside the original molecule
  • in each generation, one of the DNA molecules will be exactly the same as the original molecule
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4
Q

which bacteria was used for the Meselson and Stahl experiment + what isotope does it naturally contain

A

E.coli
- 14N (light)

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5
Q

how was the E.coli cultured

A
  • E.coli grown in a medium containing 15N (heavy), until all N-atoms are replaced by heavy isotope
  • swap bacteria to new medium with normal isotope
  • remove sample ∴ estimate relative amounts of 2 N-isotopes
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6
Q

how are proportions of isotopes estimated?

A
  • 15N are heavier than 14N, ∴ centrifuge.
  • density gradient appears
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7
Q

explain the process of DNA replication

A
  • DNA Helicase unzips DNA,
    breaking hydrogen bonds between complementary base pairs.
  • an RNA primer sequence is added. DNA Polymerase adds nucleotides with complementary bases to DNA
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8
Q
A
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