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bio 240 > topic 9 > Flashcards

topic 9 Flashcards

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Biology 101 flashcards
1
Q

history

A
  • started research in 1940s
  • studied e coli mainly
  • studied to determine practical importance of microbes
  • today study genetics to understand genetic potential of microbes
  • were able to research by comparing to mutants
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2
Q

organization of bacterial genomes

A
  • single chromosome
  • plasmids
  • bacteriophage dna also present
  • anything being replicated is a “replicon”
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3
Q

plasmids

A
  • not necessary for survival of bacteria, no “housekeeping” genes
  • typically smaller than genomes
  • however important because contain antibiotic resistance
  • regulates its own replication in cell, may be more than one copy
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4
Q

mutations

A

bacteria are ideal genetic research candidate because

  • one chromosome, so easy detection
  • nutritional mutants were used, and studied ability to produce particular nutrient or not
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5
Q

eg. Chemotaxis

A
  • capillary tube filled with nutrients
  • microbes with normal chemotaxis will move into tube due to protein
  • mutants without chemotactic protein remain outside
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6
Q

wild type

A
  • strain like one found in nature

- original isolate

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7
Q

mutant

A

strain carrying mutation relative to wild type

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8
Q

mutation

A

change in gene that disrupts function

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9
Q

allele

A

variant of gene

  • may gain function
  • may lose function
  • may change function
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10
Q

auxotroph

A

mutant is unable to make particular compound

- often cant make specific amino acid is requires

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11
Q

prototroph

A

strain capable of making all required organic compounds

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12
Q

nomenclature of genes

A
  • three letter abbreviation in lowercase italics with capital letter for separ ate genes
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13
Q

nomenclature of proteins

A
  • three letter abbreviation with first letter capitalized and capital letter to separate gene
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14
Q

genotype

A
  • description of allele in an organism
  • reflects differences of mutant from wild type
  • eg. gene involved in histidine synthesis
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15
Q

phenotype

A

observable properties of a strain

- eg. strain unable to grow in absence of histidine

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16
Q

figure 9.1

A
  • three cultures parental, mutant 1, mutant 2
  • parental is a prototroph
  • mutant 1 cant make methionine so no growth
  • mutant 2 cant make proline so no growth
17
Q

type of mutant

- change in genes

A
  • visible by changes in phenotype or growth pattern

- -> physical, visual, observable change

18
Q

selection mutation

A
  • isolating cells of a particular genotype on growth basis

- have growth advantage if will kill wild type cells

19
Q

screening mutation

A
  • identification of cells with a phenotype
  • colour, morphology, no growth
  • no advantage or disadvantage
20
Q

phenotypic selection

A
  • use of growth medium that will inhibit microbes lacking desired genes
  • antibiotic selection is commonly used
  • eg kill wild type leaving for mutant
21
Q

phenotypic screening

A
  • duplicate plates with one lacking particular nutrient
  • mutation is spotted when colony grows on full support plate, but not on partial support plate
  • kill mutant, not wild type
22
Q

replica plating

A
  • create duplicate plates

- stamps growth mediums on velvet sheet and compare growth

23
Q

patching

A
  • transfer colonies to gridded plate
  • more accurate and reproducible than standard velvet replica plating
  • pick colony with sterile toothpick, sequentially inoculate gridded test plates with picked colony and incubate, and compare growth on test plates
24
Q

types of mutation (3)

A

silent: no change in amino acid sequence
missense: change in codon that results in coding for different amino acid
nonsense: change forms a stop codon where one shouldnt be
frameshift: results in insertions or deletions of nucleotides that can alter amino acids sequences

25
Q

reversion

A

a mutation that corrects a metabolic abnormality back to wild type form

  • problematic when trying to determine mutation rates of chemical or dna exchange rates between microbes
  • -> adaptive evolution (giraffe necks)
26
Q

esther lederberg, when and how mutations occur?

A
  • created by esther lederberg
  • questioned when mutations arised
  • imprint antibiotic plate, and transfered growth onto replica plate
  • incubate replica plates
    test for streptomycin resistance
    –> since cells that werent exposed to antibiotic developed resistance, shows that mutations can arise from absence of selective agent
27
Q

luria and delbruck also aid in determining when and how mutations occur

A

show variable resistance to phage infection arises in bacteria without selective pressure
- therefore concluded that natural selection also applies to bacteria

28
Q

richard lenski

A
  • illustrated evolution
  • cultures with extended generational time without selective pressures had enhanced the ability to grow in culture compared to ones that were stored
29
Q

comparison of ancestral culture and evolved culture

A
  • mix cultures in one to one ratio
  • shows that end up with evolved cultures through natural selection,
  • relative fitness increases over time,
30
Q

relative fitness

A

ratio of number of colonies

31
Q

restriction enzymes (REs)

A
  • produced by bacteria
  • cut DNA at specific recognition site
  • recognition sites are usually palindromic (reads forwards and backwards the same)
  • similar ends of cut DNA can be paired together and ligated
  • each base should come up 25% of the time in sequence
32
Q

modification enzyme

A
  • restriction enzymes are always paired with modification enzymes
  • recognize the same site as paired restriction enzyme
  • methyltransferase activity protects dna from endonuclease activity
33
Q

dna ligase

A

the fragments are joined by dna ligase

34
Q

cloning vectors

A
  • REs allows researchers to stich together fragments of useful DNA into recombinant molecules
  • recombinant molecules can be used to clone a bacterial gene of interest
  • vectors are used to insert recombinant DNA molecules into a recipient host bacterial cell
  • plasmids
  • phages
  • cosmids
35
Q

plasmid cloning vectors

A
  • cut fragments from two plasmids carrying anti biotic resistance genes with same RE
  • transformed strain exhibited traits from both plasmids
36
Q

necessary traits

A
  • origin of replication

-

bio 240 (2 decks)

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