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BIO220 > DNA structure & replication > Flashcards

DNA structure & replication Flashcards

CH. 14

1
Q

central dogma

A

DNA → RNA → protein

(replication) transcription → translation

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2
Q

Frederick Griffith

A

Proved there is hereditary element

  • pre-biotic era
  • used mice to study S. pneumoniae
  • shiny/smooth strain = deadly
  • rough strain = killable
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3
Q

Griffith experiment

A
  1. rough strain → mouse lives
  2. smooth strain → mouse dies
  3. heat-killed smooth strain → mouse lives
  4. rough strain + heat-killed smooth strain → mouse dies

Heat-killed smooth strain mixed with rough strain caused rough strain to mutate into smooth strain

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4
Q

Avery, Macleod & McCarty

A

showed DNA is hereditary factor mentioned in Griffith experiment

  • developed transformation procedure using extract from heat killed smooth strain
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5
Q

Avery, MacLeod & McCarty experiment

A

proved DNA is hereditary element in Griffith experiment

  • treated heat-killed smooth bacteria with 3 enzymes: protease, DNase & RNase
  • result: DNase → mouse lives
  • DNA destroyed by DNase
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6
Q

protease

A

enzyme that catalyzes proteins

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7
Q

DNase

A

enzyme that catalyzed DNA

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8
Q

RNase

A

catalytic enzyme for RNA

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9
Q

Hershey-Chase experiment

A
  1. T2 bacteriophage
    • infection begins by phage attaching to bacteria cell surface
    • new phase made inside bacterial cell
    • T2 have DNA + protein (no RNA)
  2. DNA labeled with 32P
  3. proteins labed with 35P
  4. all blended
    • removes ghosts
  5. should find 32P labels in bacterial cells if DNA = hereditary material
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10
Q

what is DNA made up of?

A

phosphates

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11
Q

what is RNA made up of?

A

sulfur

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12
Q

DNA structure

A
  1. nucleotide
  2. sugar
  3. nitrogenous bases
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13
Q

nucleotide components

A
  1. sugar
  2. nitrogenous base
  3. phosphate
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14
Q

sugar components

A

1’ - base

2’ - OH or H

3’ - OH

4’ - 5’

5’ - phosphate

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15
Q

name types of nitrogenous bases

A
  1. pyrimidine - single ring
    • thymine
    • cytosine
    • uracil (RNA)
      • “Cut the Py”
  2. purine - double ring
    • adenine
    • guanine
      • “Pure things Are Good”
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16
Q

Rosalind Franklin

A

used x-ray diffraction to examine crystal strucure of DNA

  • her research used by Watson & Crick to determine DNA structure
    • uncredited
  • key findings
    • duplex
    • constant diameter
    • phosphates on outside
    • 10 bases per turn
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17
Q

Edwin Chargaff

A

found %T = %A and %G = %C

  • Watson & Crick used his research to figure out DNA structure
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18
Q

DNA characteristics

A
  1. antiparallel strands
    • 5’ to 3’ end
  2. A-T and G-C
  3. phosphodiester & hydrogen bonds
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19
Q

why are G-C bonds stronger than A-T bonds?

A

G-C bonds have 3 H-bonds while A-T bonds have 2 H-bond

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20
Q

phosophodiester bonds

A

covalent bonds btwn 2 nucleotides in nucleic acid strain

  • btwn 5-phosphate & 3-OH of adjacent nucleotide
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21
Q

pyrimidine

A

single ring

  • thymine
  • cytosine
  • uracil (RNA)

Cut the Pi – pie = 1 circle

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22
Q

purine

A

double ring

  • adenine
  • guanine

Pure things Are Good

23
Q

bacteriophage

A

(phage) virus whose host is a bacterium

24
Q

phage

A

bacteria virus

25
Q

Watson & Crick

A

proposed double helix (DNA) in 1953

  • know 1 strand, can make otro strand
26
Q

Mesellson & Stahl

A

proved DNA replication is semiconservative

  • used 14N/15N
27
Q

DNA replication process

A
  1. separate strands & keep apart
    • break bonds
    • start @ origin of replication
    • keep undwiding DNA ahead of replication complex
  2. initiate DNA synthesis
    • DNA polymerase needs primer w/ 3’-OH & ssDNA for template
  3. generate accurate DNA copy per strand
    • strands = antiparallel
    • synthesis = bidirectional
28
Q

charactericstics of origin

A
  1. A-T rich
    • less H-bonds → easier to pull apart
  2. recruits helicases to open up DNA & begin replication
29
Q

helicase

A

proteins that use ATP to break H-bonds btwn DNA strands

30
Q

single-stranded binding proteins (SSBs)

A

bind to stranded (single) regions of DNA to keep them

31
Q

how to solve supercoiling when separating strands (DNA replication)

A
  1. topoisomerase
  2. DNA gyrase
32
Q

toposoimerase

A

enzyme that cuts loop to prevent supercoiling

33
Q

DNA gyrase

A

bacterial topoisomerase

34
Q

which direction is DNA synthesized?

A

5’ to 3’

35
Q

which direction is DNA template read?

A

3’ to 5’

36
Q

DNA polymerase

A

responsible for DNA synthesis of new strands during replication & repair

37
Q

DNA primase

A

makes a short RNA primer

38
Q

DNA polymerase III

A

major DNA replication enzyme in prokaryotes

39
Q

leading strand

A

continuously synthesized strand in DNA replication

  • continues to replication bubble (5’)
40
Q

lagging strand

A

strand discontinuously synthesized

  • Okazaki fragments
  • starts @ 3’ end
41
Q

Okazaki fragment

A

short fragment of newly synthesized DNA

  • part of lagging strand
  • ligated to otro Okazaki fragments to complete lagging strand synthesis
42
Q

what is chemically happening in DNA synthesis?

A

new nucleotides are added to each strand

43
Q

deoxynucloetide triphosphates (dNTPs)

A

triphosphoate forms of deoxynucleotides

44
Q

what happens if DNA polymerase II makes a mistake?

A
  1. pause
  2. notice error
  3. takes out error
  4. redo

(proofreading)

45
Q

DNA polymerase I

A

major DNA replication enzyme that replaces primers w/ DNA

46
Q

DNA ligase

A

seals nicks in DNA

47
Q

histone

A

proteins that coat DNA

48
Q

telomere function

A
  • protect important genes
  • does not code for anything
  • has repetitive DNA @ end of chromosome
  • lose some during division
  • telomeres disappear after multiple divisions

*cancer cells = telomeres that didn’t disappear

49
Q

telomerase

A

ribonucleoprotein complex

  • RNA component
    • guides proper attachment
    • template for reverse transcription
  • protein component
    • reverse transcriptase
  • synthesizes DNA based on RNA template
    • reverse transcription
  • lenthems telomeres
50
Q

what are the most frequent mutations in cancers?

A

reactivation of telomerase

51
Q

molecular techniques

A
52
Q

spectrophotometry

A

quantify nucleic acids & proteins

  • DNA concentration & purity
  • purine/pyrimidine rings absorb UV light
  • 260mm commonly used to detect DNA
  • 280mm used to detect proteins
  • measure absorbance ratio
53
Q

restriction enzymes

A

cut DNA @ specific sites

  • Palindromic sequences - reads on both strands of DNA when read in 5’ to 3’ direction
  • some yield sticky or blunt overhangs
54
Q

vectors

A

plasmids from bacteria

  • carrier of DNA molecules
  • transfer & replicate DNA

BIO220 (1 decks)

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