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Bio 107 > Lecture 11 > Flashcards

Lecture 11 Flashcards

1
Q

3 properties of genetic material

A

1) carry info
2) replicate faithfully; transmit info
3) have variation

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2
Q

DNA was not thought to be hereditary info (up to ~70 yrs ago!) but instead ____ were.
Why?

A

Proteins

- b/c DNA has only 4 possible monomers (not a lot of combinations/ variation) but proteins have 20 possible monomers

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3
Q

Experiments (in order) discovering DNA

A
  • Griffiths Transformation Experiment
  • Avery, MacLeod, and McCarty Experiment
  • Hershey and Chase Experiment
  • Watson and Crick
  • Meselson- Stahl

G AMM HC WC MS

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4
Q

transforming principle=

A

an abiotic factor that carries hereditary info

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5
Q

Griffith’s experiment

  • question
  • experimental design
  • findings
A
  • Is there a transforming principle?
  • heat killed S strain mixed with live R-strain (neither killed the mouse separately) kills the mouse
  • there’s an abiotic transforming principle (DNA or protein)
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6
Q

Avery, MacLeod, and McCarty Experiment

  • question
  • experimental design
  • findings
A

-Q: what is the transforming principle?
- exp: repeated Griffith’s experiment and added enzymes to specifically degrade different macromolecules
If DNA is degraded, mouse lives
- Finding: DNA is the transforming principle

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7
Q

Hershey and Chase Experiment

  • question
  • experimental design
  • findings
A
  • Is DNA the universal transforming principle?
  • exp: used phase and radioactivity to differentiate label proteins vs DNA
    S35= proteins
    P32= DNA
    S35 labelled phage: radioactivity is in the supernatant, not the pellet
    P32 labelled phage: viral DNA enters the bacterial cell, and the pellet is now radioactive
    Conclusion: DNA is the universal transforming principle
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8
Q

Watson and Crick discovered:
(3 things)
by using the ____ rule and the x-ray crystallography images by _____ ___

A
  • DNA is double helix
  • sugar-phosphate backbone
  • complementary base pairing (A to C and C to G)
  • Chargaff’s rule
  • Rosalind Franklin
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9
Q

What 3 forces stabilize DNA?

A

1) phosphodiester bonds= covalent bonds that form the backbone
2) H-bonds: base pairing
3) Hydrophobic base stacking

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10
Q

DNA replication happens in the __-phase of the cell cycle

A

S phase

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11
Q

List Meselson-Stahl’s 3 possible models for DNA replication

A
  1. Conservative
  2. Semi conservative
  3. Dispersive
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12
Q

describe the conservative DNA replication model

A

the entire parent is photocopied

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13
Q

describe the semi-conservative DNA replication model

A

each parent strand acts as a template for daughter strand synthesis

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14
Q

describe the dispersive DNA replication model

A

analogy: photocopy, throw pages in the air and hope they come down with one page in each version
- bad model- very inefficient
- each molecule is a random collection of parent/ daughter

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15
Q

How did Meselson-Stahl determine that semiconservative DNA replication was correct?

A

used radioactivity to change the molecular mass of nitrogen

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16
Q

all nucleic acids are polymerized by adding nucleotides to the __ end

A

3’

3’ OH

17
Q

the enzyme of DNA replication is __ ______ which:

A

DNA polymerase

- catalyzes phosphodiester bond formation

18
Q

substrate of DNA replication is ___

- the energy for replication comes from hydrolysis of __

A

dNTPs (where N is replaced with A, C, T, or G)

Pi

19
Q

___ _____ gives specificity

A

base pairing

20
Q

the leading strand is synthesized in the same direction as __ ___

A

fork opening

21
Q

the lagging strand is synthesized in the ____ direction of fork opening

A

opposite

22
Q

what happens in the initiation step in dna replication

A
  • DNA helicase unwinds the double helix (at the origin or replication) after the initiation protein attracts it
  • the single strands are now templates
  • Primase synthesizes the RNA primer and DNA polymerase III will start adding nucleotides (5’ to 3’ direction)
  • SSBs keep the bubble unwound by staying in the replication forks
23
Q

what happens in the elongation step in dna replication

A
  • complementary base pairing occurs and DNA polymerase III catalyzes the actual joining of the nucleotides
  • they’re linked through phosphodiester bonds in a process called polymerization
  • DNA pol I removes the primer and DNA ligase connects the spaces (fills in Okazaki fragments)

Bio 107 (12 decks)

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