DNA Replication Flashcards

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1
Q

5 words

A

semi conservative
anti parallel
complementary
New DNA from 5’ to 3’
a fork is 1/2 a bubble

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2
Q

What happens at initiation?

A
  1. Begins at origin
  2. DNA gyrase unwinds doube helix
  3. DNA helicase breaks double strand into single strand forming bubbles
  4. Single stranded binding proteins attach to the free DNA sections to prevent re-annealing
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3
Q

Where does initiation begin?

A

Origins: specific points on chromos
- Prokaryotes have 1 per chromosome
- Eukaryotes have multiple which speeds up replication

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4
Q

What unwinds DNA double helix?

A

DNA Gyrase enzyme

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5
Q

What separates DNA double strand?

A

DNA helicase breaks H-bonds between bases

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6
Q

What prevents the double helix from reforming during initiation?

A

SSBP - prevent re-annealing

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7
Q

What happens at elongation?

A
  • RNA primase attaches to parent strand and lays down RNA nucleotide(s) (primer)
  • DNA polymerase III attaches to 2 parent strands’ primer and attaches complementary bases from 5’ to 3’
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8
Q

Leading strand

A
  • RNA primase attaches to 3’ end of parent strand and puts down RNA nucleotide
  • DNA polymerase III binds to RNA primer and begins adding complementary nucleotides TOWARDS the fork
  • When poly 3 reaches the end of the fork, DNA polymerase I dismantles the primer and replaces it with DNA nucleotides
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9
Q

Lagging strand

A
  • RNA primase attaches to parent strand and puts down RNA nucleotides
  • DNA polymerase III binds to RNA primers and begins adding complementary nucleotides in 5’ to 3’ direction AWAY the fork
  • poly 3 continues until it reaches another primer then detaches
  • another RNA primer and poly III attach and add nucleotide upstream to (closer to fork)
  • RESULT: discontinuous pieces called OKAZAKI FRAGMENTS
  • Poly 1 removes the primers and replaces for DNA nucleotides
  • DNA ligase then joins the OKAZAKI fragments with phosphodiester bonds
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10
Q

ORDER OF ENZYMES LEADING

A

RNA primase
DNA Polymerase III
DNA Polymerase I

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11
Q

ORDER OF ENZYMES LAGGING

A

RNA primase
DNA Polymerase III
DNA Polymerase I
DNA ligase

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12
Q

What happens during termination?

A
  • DNA automatically goes back to helix
  • Lagging strand and leading strand uneven due to RNA primers so it is snipped off
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13
Q

What is a telomere?

A
  • end of chromosome that holds useless info
  • buffer loss of DNA which takes place at termination
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14
Q

What happens when telomere gone? what happens telomere regen cant be shut off?

A
  • telomere gone = dead cell
  • telomere stays alive forever = cancer cell
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15
Q

Proofreading

A
  • poly II checks to make sure H-bonds between base pairds are present.
  • If not, enzyme removes new nucleotide and inserts the right one
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16
Q

Why do we need DNA replication?

A

Growth, reproduction, repair