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Biology 1202 > DNA > Flashcards

DNA Flashcards

1
Q

What is the genetic material?

A

DNA

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2
Q

What are the 3 keY experiments in determining DNA was the genetic material?

A
  1. Griffith experiment 1928
  2. Avery, McCarty & Macleod 1944
  3. Hershey & Chase 1952
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3
Q

What are the key aspects to the Griffith experiment?

A
  • Mice infected with R- or S- strains of pneumonia. R-strains could be transformed to ‘S’ by transforming principle, which therefore must be the genetic material
  • Transforming principle was the genetic material but did not know what the material was
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4
Q

What are the key aspects to the Avery, McCarty & Macleod experiment?

A
  • Continuing Griffith experiment, they investigated which component of S-strain extract was transforming principle
  • RNA was unable to transform R strain to S strain
  • BUT DNA could transform R strain to S strain
    DNA is genetic material
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5
Q

What are the key aspects to the Hershey & Chase experiment?

A
  • Radio-Labelled protein coat & DNA of Phages
  • 32S labeled proteins (stayed outside E.Coli cells)
    32P labeled DNA (entered E.Coli cells)
  • Confirmed DNA was genetic material
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6
Q

In the Griffith Experiment, which combinations resulted in a dead mouse?

A

A. Live Smooth bacteria
B. Heat-killed Smooth bacteria plus Live Rough bacteria

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7
Q

DNA and RNA are both polymers of?

A

Nucleotides

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8
Q

Nucleotides are composed of?

A
  1. 5-carbon sugar
  2. 1- 3 phosphate group(s)
  3. Organic nitrogenous base (all covalently linked)
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9
Q

Nucleotides are disinguished by what bases?

A

dATP, dTTP, dCTP, dGTP

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10
Q

What type of bond links nucleotides together in a CHAIN?

A

Phosphodiester bond (strong): Form the backbone of DNA and RNA

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11
Q

What is Chargaff’s rule?

A

This rule implies base pairing
A = T
G = C

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11
Q

What is the chemical nature of nucleic acids and describe them?

A
  1. Pyrimidines - smaller bases, single rings (cytosine and thymine)
  2. Purines - larger bases, double rings (adenine and guanine)
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12
Q

Who are the scientists who researched the three-dimensional structure of DNA?

A
  1. Wilkins and Franklin
  2. Watson and Crick
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12
Q

What did Wilkins and Franklin do?

A
  • They deduced DNA is a spiral structure using X-ray diffraction
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13
Q

What did Watson and Crick do?

A
  • They deduced that DNA is an intertwined double helix
  • Complementary base-pairing
    Purines pair with pyrimidines
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14
Q

What is the name for the orientation of two strands of DNA double helix running in opposite directions?

A

Antiparallel configuration

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15
Q

What bonds occur between complementary base pairing?

A

Hydrogen bonds

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16
Q

In replication, what are the 3 models?

A
  1. Conservative
  2. Dispersive
  3. Semiconservative
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17
Q

Melson & Stahl showed that DNA replication occured in what manner?

A

Semi-conservative manner - Meaning one strand is a parental strand (old), and one strand is the daughter strand (new)

18
Q

What is the role of DNA polymerase III?

A
  • Adds nucleotides to build new DNA strands. - Nucleotides are added according to base pairing, H bonds
  • Synthesis 5’ to 3’
19
Q

What is the replication orgin?

A

This is where replication of DNA begins at one or more sites

20
Q

Opening of DNA double helix is the process called?

A

Helicase (initiates replication and unwinding at replication orgin, creates replication fork)
Powered by ATP

21
Q

What do SSB proteins stand for and their role in replication?

A

SSB Proteins (single stranded binding proteins)
- They stabalize single strands and prevent them from rejoining

22
Q

What is th name for this process of relieving torque/tension and remviung torsional strain created by opening of the double helix?

A

Gyrase or topoisomerase

23
Which direction does the parent strand go? Which direction does the daughter strand go?
Parent strand (template) 3' to 5' Daughter strand 5' to 3'
24
What is the role of primase in DNA replication?
- Builds a primer made of RNA
25
What process removes the primer and replaces it with DNA?
DNA Pol I - Process that cuts out RNA and replaces it with DNA using polymerization activity
26
What is the role of ligase in DNA replication?
Joining of Okazaki fragments and joins newly synthesized DNA at origins of replication
27
What is the sliding DNA clamp?
- Protein attached to DNA pol III, encircles DNA &Tethers DNA pol III to template strand
28
Which strand is continuous vs discontiuous?
Leading strand (top) - Continuous Lagging strand (bottom) - Discontinuous
29
What is it called when the wrong nucleotide is added?
Base-Pair mismatch
30
What is the role of proofreading in errors of DNA replication?
- DNA Polymerase itself “proofreads” the newly made DNA - It reverses direction, excises the wrong nucleotide, adds the correct base pairing, and continues synthesis
31
What is the role of DNA repair mechanisms in errors of DNA replication?
- They scan the newly synthesized DNA and excise any mismatches that were missed by DNA polymerase - It locates distorton, removes it, DNA pol fills in gaps, and ligase seals it
32
What is the process that prevents chromosome shortening?
Telomerase
33
What is the difference between telomere and telomerase?
Telomere: Region of non-coding repeat DNA sequences found at the end of chromosomes; protects genes found near chromosomes ends by providing “buffer zone” Telomerase: Enzyme that adds DNA to the end of chromosomes to maintain the “buffer zone” of telomeres; it has its own RNA template. It binds to the 3' end
34
What is the 3'overhang?
The 3'overhang is when there is no where to put a primer so DNA Pol III can NOT add nucleotides
35
DNA polymerase adds nucleotides to which end of the strand?
3'
36
What does Hayflick's limit state?
- Hayflick’s limit: Human cells can only divide a certain number of times before dying cells taken - Cancerous cells have restored telomerase activity do NOT show Hayflick’s limit
37
What is the chromatin?
Chromatin = DNA + associated proteins
38
What is the nucleosome?
Nucleosome - DNA wrapped around 8 histones
39
Okazaki fragments form on the what strand?
Lagging strand
40
DNA polymerase III can only add nucleotides to an existing chain, therefore what is required?
A primer (brief RNA sequence) is required
41
What are the order of events in which DNA replication occurs of the lagging strand?
1. Replication proteins bind to and activate the origin of replication 2. Helicase unwinds the double helix 3. SSBPs stabilize and hold the single strands apart 4. Primase synthesizes an RNA primer 5. DNA pol III adds DNA nucleotides to the primer 6. DNA pol I replaces the RNA primer with DNA 7. DNA ligase joins Okazaki fragments together
42
If one strand of a DNA molecule has the base sequence 5'ATTGCAT3', its complementary strand will have the sequence?
3' TAACGTA 5'
43
If one strand of a DNA molecule has the base sequence 5'AATACGG3', its complementary strand will have the sequence?
5' CCGTATT 3' or 3' TTATGCC 5'

Biology 1202 (4 decks)

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