Microbiology Chapter 8

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amanda430
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265059
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Microbiology Chapter 8
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2014-03-06 13:10:33
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Microbiology Chapter 8
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Microbiology Chapter 8
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  1. What is natural selection?
    the process of adapting to survive
  2. What is a genotype?
    Sequence of nucleotides in DNA
  3. What is a phenotype?
    Observable characteristic of genes
  4. What are the 2 ways genetic change occurs?
    • mutation
    • horizontal gene transfer
  5. What is mutation
    changing of the organism's existing nucleotide sequence
  6. What is horizontal gene transfer?
    Acquisition of genes from another organism
  7. What is spontaneous mutation?
    genetic changes that are a result of normal processes
  8. What is the mutation rate range?
    10^-4 - 10^-12
  9. What is reversion?
    When a mutation is passed onto a daughter cell and is then mutated back to it's non-mutant form
  10. What is base substitution?
    most common mutation, occurs during DNA synthesis when an incorrect nucleotide is incorporated
  11. What is point mutation?
    when only one base pair is changed
  12. What are the three possible outcomes of mutation?
    • Silent mutation
    • missense mutation
    • nonsense mutation
  13. What is a silent mutation?
    Mutation doesn't effect the phenotype
  14. What is a Missense Mutation?
    • When an altered codon specifies a different Amino Acid
    • In most cases the cell grows slowly due to the faulty protein
  15. What is a nonsense mutation?
    Occurs when the altered codon is a stop codon
  16. What is a frameshift mutation?
    When +/- one of more nucleotide pair changes the mRNA reading from
  17. What are transposons?
    Segments of DNA that can move between segments in a cell's genome
  18. What is a mutagen?
    • an outside influence¬†
    • ex. radiation
  19. what is an induced mutation
    occurs in reaction to a mutagen
  20. What is a base analog?
    compound that structurally resembles a nucleobase closely enough to be incorporated into a nucleotide in place of a natural nucleotide
  21. What is an auxotroph?
    when a mutation creates the need for a growth factor
  22. What is a wild type?
    the cell that occurs naturally
  23. What are the 3 possible outcomes of point mutation?
    • Silent
    • Missense
    • Nonsense
  24. What is a silent mutation?
    causes no change in AA or protein
  25. What is a missense mutation?
    Changes the AA
  26. What is a nonsense mutation?
    Causes a premature stop codon
  27. What is Transposons?
    A jumping gene that disrupts gene expressions
  28. What are the two main mutagens?
    Chemical and radiation
  29. What does a chemical mutagen cause?
    Base substitution or frameshift
  30. What does an akylating agent do?
    Changes the base structure so it binds to a different base
  31. What is a base analog?
    resembles a nucleobase, but pairs with a different base
  32. What are the two types of radiation?
    UV and X rays
  33. What do UV Rays cause?
    Thymine dimers
  34. What do X-rays cause?
    Break is DNA, often produces lethal deletions
  35. What are the 2 mechanisms that help repair damaged DNA during replication?
    • Proofreading
    • Mismatch Repair
  36. What enzyme is used during proofreading?
    DNA polymerase
  37. What does mismatch repair do?
    • fixes errors missed by DNA polymerase
    • recognizes new strand that contains no methyl groups and cuts out a portion of incorrect DNA
  38. What is the enzyme that helps with repair of modified nucleobases in DNA?
    glycosylase
  39. What are the three ways that thymine dimers are repaired
    • Photoreactivation
    • Excision Repair
    • SOS Repair
  40. What is photoreactivation?
    • repair of thymine dimers via light energy
    • light energy breaks down dimer
  41. What is excision repair?
    • repair of thymine dimers via dark repair
    • enzyme removes damaged DNA and polymerase repairs
  42. What are the two approaches to mutant selection?
    • Direct
    • Indirect
  43. What is Direct mutant selection?
    a medium that allows the mutant to grow, but not the parent
  44. What is indirect mutant selection
    • replica plating
    • velvet plating procedure
  45. What is penicillin enrichment?
    • Add cells to a broth medium, allow wild types to thrive, mutants to stall
    • add penicillin to kill off growing cells¬†
    • add penicillinase to kill of penicillin, leaving mutants
    • plate mutants onto complete medium to grow
  46. What is the Ames Test?
    screening for possible carcinogens
  47. What is the process of the Ames Test?
    • involves his- salmonella auxotroph, which is susceptible to mutation to his+ salmonella prototroph
    • if mutation occurs then mutagen is added to liver extract to see if it's a carcinogen
  48. What is horizontal gene transfer?
    acquiring genes from other cells
  49. What is homologus recombination
    When new genes become incorporated into host chromosome
  50. What are three methods that genes can be transferred by?
    • transformation
    • transduction
    • conjugation
  51. What is transformation?
    the uptake of naked DNA by bacteria
  52. What is transduction
    Bacterial DNA transfer via a virus
  53. What is conjugation?
    DNA transfer between bacterial cells
  54. Explain transformation
    naked DNA that is in the environment from a lysed cell is taken up by "competent" bacteria
  55. Explain transduction
    • transfer of genes via a bacteriophage
    • bacteriophage accidently takes up Bacterial DNA during synthesis and transfers it to another bacterial cell
  56. Explain conjugation
    • Transfer of DNA via a sex pilus
    • example is f-, f+, and f`
  57. What is the mobile gene pool
    variation of genes within a population
  58. What is an insertion sequence transposon?
    integrates via transposase enzyme
  59. What is composite transposon?
    1+ genes, integrates via non-homologus recombination

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