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MIMG 101 > Midterm 2 > Flashcards

Midterm 2 Flashcards

1
Q

Antibiotics against bacterial transcription/translation

A
  • rifamycin: binds to RNA polymerase
  • streptomycin: inhibits peptide initiation and elongation
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2
Q

Inducible Operon

A
  • turned on by substrate
  • usually off
  • catabolic operons: breaks down nutrients (lac operon)
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3
Q

Repressible Operon

A
  • turned off by product synthesized
  • usually on
  • anabolic operons: enzymes required to synthesize an amino acid stop when no longer needed to be produced (arg operon)
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4
Q

Structure of Operon

A
  • regulator: gene encoding for repressor protein (on/off switch)
  • control locus: promoter locus (binds RNA polymerase) and operator locus (binds the repressor)
  • structural locus: actual gene transcribed
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5
Q

lac operon

A
  • lactose metabolism in e.coli (not e.coli’s first nutrient - glucose is first)
  • can be induced on a spectrum
  • lactose concentration removes repressor and allows transcription
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6
Q

arg operon

A
  • regulates arginine synthesis
  • excess nutrient binds to repressor and activates it
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7
Q

Causes and effects of mutations

A
  • causes: spontaneous (random changes arising from error - fluctuation test) or induced (exposure to known mutagens - ames test)
  • effects (positive or negative) - mutations are permanent, mainly harmful - can still provide adaptive advantages like antibacterial resistance
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8
Q

Ames test

A
  • screens mutagenic/carcinogenic compounds
  • organism: salmonella typhimurium mutant -> lost the ability to synthesize histidine. (mutation is susceptible to back mutation)
  • mutant plated on media with minimal histidine (one sample has mutagen and the other is normal)
  • high number of revertant (reverts back to natural) means exposed chemical is mutagenic
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9
Q

Fluctuation test

A
  • tests for randomly occuring mutation (mutations don’t need to occur by selective agent)
  • organism: streptomycin-sensitive organisms
  • one sample is cultured in large flask of medium and another is inoculated in 100 tubes of medium
  • large flask ~ approximately same number of restant colonies on each plane (always mixing allows even spread of antibiotic resistance)
  • inoculated 100 tubes: number of resistant colonies varies widely from plate to plate
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10
Q

Horizontal Gene Transfer

A
  • movement of any genes between organisms
  • G/C content: if there is a large genomic island that is different from core genome and is flanked by direct repeats indicate HGT
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11
Q

Transformation Experiment - mice

A
  • Fredrick Griffith (1928)
  • organism - streptococcus pneumoniae
  • four mice injected with rough strain (nonvirulent), smooth strain (virulent), heat-killed smooth strain, and rough strain inoculated with heat killed smooth strain
  • shows that bacteria can take up something to become virulent
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12
Q

Transformation Experiment - bacteria

A
  • Avery & McCarthy (1941)
  • Demonstration that DNA is genetic material
  • s. pneumoniae is naturally competent (which is rare) - able to take up DNA from environment
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13
Q

Gram-positive DNA transformation

A
  • dsDNA enters transformasome (DNA binding protein + pore)
  • DNA is sucked inside and nuclease makes it ssDNA
  • ssDNA is taken by RecA for homologous recombination
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14
Q

Gram-negative DNA transformation

A
  • pilus binds to dsDNA
  • dsDNA becomes ssDNA in periplasm
  • other steps are similar to gram positive transformation (RecA recruits ssDNA to homologous site)
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15
Q

Bacteria competency

A
  • naturally competent
  • artificially: induced by electroporation or calcium chloride
  • acquired: reponse to signals
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16
Q

Conjugation experiment - bacteria

A
  • lederberg and tatum (1946)
  • e.coli nutritional mutatants
17
Q

Conjugation experiment - cell to cell contact

A
  • U-shaped tube with glass filter only for DNA
18
Q

HFR

A
  • f-plasmid integrates into the chromosome rather than having f-plasmid free forming like normal
  • hfr cell brings parts of chromosome into recipient cell
  • recipient cell can’t become donor under hfr because the chromosome transfer is incomplete (could be missing gene necessary for conjugation)
19
Q

Transposable Elements

A
  • DNA moving within organism genome
  • surrounded by repeats
  • replicative: gene can be replicated in orignal and target
  • conservative: gene only enters target - not in both spots
20
Q

Generalized Transduction

A
  • pure bacterial DNA is integrated in a bacteriophage capside
  • same generation transfer of bacterial DNA
  • lytic stage
21
Q

Specialized Transduction

A
  • lysogenic first: phage is integrated into DNA and will replicate
  • when environmental stress occurs, changes into lytic phase
  • phage genome excised incorrectly so transduced bacteria isn’t pure
22
Q

How to determine evolutionary history/ what is a good biological clock?

A
  • need a gene/protein that all organisms have
  • is highly conserved with a slow mutation rate
  • functionally constant
  • e.g 16S rRNA
23
Q

3 domains of life

A
  • Carl Woese
  • Archaea, Bacteria, Eukarya
24
Q

Phylogenetic trees - key terms

A
  • root - initial ancestor
  • node - ancestor relating branch of the tree
  • monophyletic clade - all from the same ancestor
25
Q

Viral Structure

A
  • viroid - genome/nucleic acid
  • virion - capsid (protein layer) + viroid
  • sheath and tail fibers (bacteriophage)
  • membrane (developed from previous host cells which aid in protection, binding, and entry)
  • Symmetrical viral structure: isosahedral and filamentous
  • Asymmetrical viral structure: membrane viruses
26
Q

Phage Therapy Advantages

A
  • Specific targeting only certain bacterial species
  • Replicate at site of infection to amplify effects
  • Active against antibiotic resistant bacteria
  • Phages can evolve to overcome bacterial resistant mechanisms (******phage-host arms race******)
27
Q

Phage Therapy Disadvantages

A
  • development of phage resistance (********phage-host arms race********)
  • development of phage neutralizing bacteria
  • not accessible to intracellular pathogens
  • can transfer toxin genes that make bacteria more pathogenic by inducing lytic phase
  • bacteria can also use **********restriction endonuclease************ to cleave unprotected phage DNA that renders it inactive. they may also have methylated (limits transcription) recognition sites so phage DNA can’t integrate.
28
Q

CRISPR - Cas9

A
  • originally inherent to bacteria - primative adaptive immune system
  • Clustered Regularly Interspaced Short Palindromic Repeats
  • repeats and spacers which don’t code for anything but it is near gene coding of proteins for cleavage - Cas9
  • finds specific PAM sequence and cuts upstream
29
Q

CRISPR - biofilm

A
  • WT lysogenized strain showed no biofilm formation. Cas gene deleted strain showed biofilm formation (crystal violet stain). Reintroduced Cas gene strain showed restoration of antibiofilm phenotype.
  • This ensures that phage produced by lysogen bacteria isn’t contained within a biofilm and can’t kill the rest of the community.
30
Q

Four Chains of Infection

A
  1. Organism (virulence factor)
  2. Reservoir (where you find the microbe multiplying but may not be infecting): humans/animal/water/environment
  3. Transmission: modes of transmission discussed above
  4. Susceptible host: enter through portal of entry and depends on immunocompetence of host
31
Q

Epidemiology Vocabulary

A
  • Prevalence: proportion of cases in a population at a given time and place
  • Incidence rates: number of new cases of disease per susceptible people (excludes those already sick) per year
  • Morbidity rate: incidence of all diseases in a population
  • Mortality rates: number of deaths per number of cases of dease in an area
32
Q

HIV

A
  • HIV is a special RNA virus
    • retrovirus: uses reverse transcriptase to copy RNA genome into DNA and insert viral DNA into host genome → life-long infection
    • viral genome is surrounded by capsid as well as envelope with a protein layer → protein fit well into CD 4 receptor proteins
      -
33
Q

HIV progression to AIDS

A

CD-4 t-cells decreases as time of infection increases
- Opportunistic disease often are the cause of death for individuals with AIDS as they take advantage of the weakened immune system
- Not all individuals with HIV progress to AIDS as there are therapies that keep CD-4 T-cell counts high

34
Q

Taxonomy

A
  • Classification of Organisms
  • Microscopy - physical properties
  • Enzymology - how they got and used energy
  • Molecular biology - how close their gene sequences are
35
Q

Phylogeny

A
  • classification of organisms by evolutionary relatedness
  • 16S RNA

MIMG 101 (12 decks)

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