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Genetics > Experiments notes pages 1-16 > Flashcards

Experiments notes pages 1-16 Flashcards

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Biology 101 flashcards
1
Q

Genetic Material

A

Carried on chromosomes (proteins + DNA)

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2
Q

Protein = Variability

A

20 amino acids –> proteins
4 nucleotides –> DNA

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3
Q

The orignial hypothesis was that DNA is made of _____

A

Proteins

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4
Q

Who rejected the hypothesis that DNA is made from proteins

A
  1. Griffith (1928)
    Avery et al (1944)
  2. Hershey and Chase (1952)
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5
Q

Griffith used Strep pneumoniae. What were the 2 strains?

A

Smooth (S)
Rough (R)

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6
Q

What is Smooth strain?

A

-colonies smooth/shiny
-cells are enclosed in polysaccharide capsule
-virulent (infectious)
-wild type

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7
Q

What is Rough strain?

A

-no polysaccharide capsule
-nonvirulent (easy to engulf and destroy)
-mutant

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8
Q

What were the 4 different flasks Grifith used and what were the outcomes of each?

A
  1. S (virulent) –> dead mouse recovered S
  2. R (non virulent) –> alive mouse
  3. Boiled S (virulent) –> alive mouse
  4. Boiled S + Living R –> dead mouse recovered S
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9
Q

Are living cells necessary for virulence?

A

Yes

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10
Q

Transformation in Griffiths experiment was?

A

Conversion of Rough –> Smooth

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11
Q

What was Avery et al experiment?

A

Boiled S split into 3 samples. Each one was added either
RNase - destroys RNA
Protease - destroys protein
DNase - destroys DNA

Then each was added to living R flask

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12
Q

Transformed bacteria remained virulent in subsequent generations sooo ???

A

Transformed traits are heritable

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13
Q

What is Transforming Principle made of?

A

DNA

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14
Q

What happened to all 3 flasks that Avery made?

A

The one with RNA killer transformed
The one with protein killer transformed
The one with DNA killer did not transform

So DNA is transforming principle and is neededdd

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15
Q

What is Hershey and Chase Experiment?

A

studied Bacteriophage T2 (50% protein 50% DNA)
- used radioactive labeling to “see” molecules
- sulfur (35S) marks protein
- phosphorus (32P) marks DNA

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16
Q

What are the infection steps for Hershey Chase?

A
  1. adsorption - phage attaches to bacteria via tail fibers
  2. phage material (must be genetic material) enters bacteria (production of nre viruses within bacterial cell)
  3. bacterial lysis (new phage progeny released)
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17
Q

What was Hershey and Chase experiment to see what is the genetic material?

A

Kitchen blender
1 phage labled 35S for protein
1 phage labeled 32P for DNA
infect ecoli
blend - shear protein coats
spin - separate protein coats and cells
infected bacteria will pellet
32P pellets so DNA is genetic material

18
Q

What is DNA made of?

A

Phophate + Sugar + Base

19
Q

A + G = how many rings?
C + T = how many rings?

A

AG = 2
CT = 1

20
Q

What is deoxyribose?

A

-every base has OH except 2’
-1’ N base attached
- 3’ has OH
- 5’ Phosphate attached

21
Q

What did Watson and Crick do?

A
  • Structure of DNA
  • Double Helix
  • 5’ phosphate linked 3’ OH via covalent bonding
22
Q

What did Erwin Chargaff do?

A

Total purines = Total pyrmidines
T = A & G=C

23
Q

What did Rosalind Franklin/Maurie Wilkins do?

A

DNA = 2 parallel parts = helical
helix = 10 turns
measured helix diameter

24
Q

How many hydrogen bonds for
AT
GC

A

2 for AT
3 for GC

25
Q

What aspect of its structure causes DNA to migrate to the positive pole?

A

”-“ charge on outside drives DNA to (+) pole

26
Q

What is
Complementary Strand
Specific Base Pairing

A

each strand a template for another

only one sequence possible for template

27
Q

What are 3 models of DNA replication?

A

Conservative - 2 new + 2 old
semi conservative - 1 new 1 old + 1 new 1 old
dispersive - 2 mixed + 2 mixed

28
Q

Where are sugar-phosphate backbones located?

A

outside of helix
covalent bonds between sugar and phosphate hold nucleotides together

29
Q

What are 3 different forms of DNA?

A

A form -
less hydrated,
more compact,
right-handed,
seen in high salt

B form -
more hydrated
less compact
right-handed
found in vivo
Watson and Crick

Z form
left handed
zig zag sugar phosphate backbone
seen in short DNA pieces with alternating purine/pyrmadine

30
Q

What is Oligonucleotide?

A

short chain of nucleotides
single stranded DNA

31
Q

What is Denaturing?

A

separating 2 strands of DNA also called melting. Heating DNA breaks H bonds.

G/C rich DNA higher melting temp because it had 3 H bonds

32
Q

What is hairpin/stemloop?

A
  • sequences on same strand are inverted complements
  • sequence between inverted repeats forms loop
33
Q

What is Stem?

A

no loop

34
Q

What were the 2 experiments to test which model of DNA replication?

A

Meselson- Stahl (prokaryotes)
Taylor (Eukaryotes)

35
Q

What was Meselson-Stahl experiment?

A

-studied ecoli
-heavy isotope 15N to label DNA
- N14 is light/normal

36
Q

What is a density gradient centrifugation?

A
  1. DNA extracted from cells, cut into pieces and added to gradient
  2. centriguged high speed
  3. equilibrium means DNA concentrates within gradient where density equivalent to CsCl
  4. See DNA by staining with ethidium bromide and shining UV light
37
Q

What were results at time = 1 for meselson-stahl?

A

DNA in middle of tube indicating cannot be conservative method because they are together

38
Q

What were results at time = 2 for meselson-stahl?

A

DNA in middle and in Light/Light indicating that it is semi-conservative.

39
Q

What was Meselson-stahls experiment?

A

put ds DNA in 14N and then gradient centrifuge to see what type of DNA it is

40
Q

What was Taylors Experiment?

A

-studied bean root tips
-followed cells through 2 rounds of mitosis
-labeled DNA with titrated 3H thymidine (radioactive)

41
Q

What was the method of Taylors Experiment?

A

G1 –> Sphase replication with 3H –> G2, Prophase at Metaphase Autoradiography

After Mitosis –> 1 daughter cell —> S phase

Genetics (6 decks)

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