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Microbio 3220 > Exam 3 - Lecture 17 > Flashcards

Exam 3 - Lecture 17 Flashcards

1
Q

what is the most common type of mutation?

A

point mutation

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2
Q

what are the two types of point mutations?

A
  • SNPs (single nucleotide polymorphism; single nucleotide is changed)
  • Indels (insertion or deletion of nucleotides)
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3
Q

consequence of mutations depends on:

A
  • type (SNP, indel, etc.)
  • location (within a gene, between two genes)
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4
Q

what does CDS stand for?

A

coding DNA sequence

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5
Q

what does IG stand for?

A

intergenic

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6
Q

what can a SNP mutation in a CDS result in?

A
  • silent mutation
  • missense mutation
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7
Q

what can an indel mutation in a CDS result in?

A

frameshift mutation

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8
Q

what is a silent mutation?

A

no amino acid change i the resulting polypeptide

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9
Q

what is a missense mutation?

A

amino acid change in the resulting polypeptide

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10
Q

what is a frameshift mutation?

A

multiple amino acid changes/early stop codon

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11
Q

what does a point mutation in an IG cause?

A
  • usually no effect
  • can alter gene expression if in an area like a promoter
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12
Q

what is mismatch repair and what enzyme carries out this process in E. coli?

A
  • a type of excision repair
  • mismatch correction enzyme (MutS) scans newly synthesized DNA for mismatched pairs
  • mismatches are removed and repaired by DNA pol and DNA ligase
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13
Q

in E. coli, new strands will be ___________ and old strands will be __________ to distinguish between them for mismatch repair.

A

unmethylated; methylated

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14
Q

will mismatch repair be carried out on a methylated or unmethylated strand?

A

unmethylated

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15
Q

do eukaryotes undergo vertical or horizontal gene transfer? how about prokaryotes?

A
  • vertical: euks
  • horizontal: proks
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16
Q

true or false: horizontal gene transfer can allow gene transfer between different species.

A

true

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17
Q

for HGT DNA to be inherited by offsrping, it must become _______ and find a way to ___________

A

stable; replicate

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18
Q

what are two ways HGT DNA can become stable once trasnferred?

A
  • self replication
  • integrate into the chromosome
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19
Q

what is recombination?

A

integration of transferred DNA into the host genome

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20
Q

what are two major types of recombination?

A
  • homologous recombination
  • site specific recombination
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21
Q

what are the three important differences between site specific has from homologous recombination?

A
  • it does not require long regions of DNA homology
  • recombination occurs at specific target sites in DNA molecules
  • mediated by specific enzymes called recombinases
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22
Q

what are two major types of transmissible DNA?

A
  • transposable elements
  • plasmids
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23
Q

what are three mechanisms for horizontal gene transfer?

A
  • conjugation
  • transformation
  • transduction
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24
Q

which domains of life have transposable elements?

A

all three

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25
Q

what is transposition?

A

small segments of DNA moving about the genome (they are sometimes called jumping genes)

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26
Q

who discovered transposable elements?

A

Barbara McClintock in 1940s

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27
Q

what are the simplest transposable elements?

A

insertion sequences (IS)

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28
Q

what are composite transposons (Tn)?

A

transposable elements containing “extra” genes flanked by two insertion sequences

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29
Q

what are unit transposons?

A
  • they are between being an IS and a composite Tn
  • it’s like an extended IS than can contain extra genes
  • basically a gene flanked by ONE transposase gene
30
Q

what are inverted repeats? what do they mark?

A
  • short stretches of identical nucleotides in opposite orientations
  • marks the ends of the IS or Tn
31
Q

what is transposase?

A

an enzyme responsible for site specific transposition

32
Q

what are direct repeats?

A
  • host DNA that is the site for insertion
  • duplicated during insertion
33
Q

what are the two types of transposition?

A
  • simple transposition (cut and paste)
  • replicative transposition (copy and paste)
34
Q

what are retrotransposons?

A

RNA copy of the transposable element is made and is transcribed back into DNA to integrate at the new site

35
Q

what are plasmids?

A
  • small, extrachromosomal circular DNA molecules
  • exist and replicate independently of chromosome
  • contain non-essential genes that confer selective advantages to the host (drug resistance, virulence, etc.)
36
Q

true or false: cells cannot have more than one plasmid.

A

false

37
Q

what are episomes?

A

plasmids that can integrate reversibly into the host chromosome

38
Q

what are conjugative plasmids?

A

plasmids that can transfer copies of themselves to other bacteria during conjugation

39
Q

true or false: plasmids can exist independently of the host chromosome.

A

true

40
Q

what structure facilitates conjugation?

A

sex pilus/F pilus

41
Q

true of false: donor chromosomal genes are usually transferred during conjugation.

A

false; they aren’t (usually)

42
Q

plasmids are replicated via what method?

A

rolling circle method

43
Q

at the end of successful F+ x F- mating, what types of cells are present at the end?

A

two F+ cells

44
Q

what is the synthesis of the complementary strand in rolling circle replication similar to?

A

similar to lagging strand synthesis

45
Q

in the rolling circle method, which end of the nicked plasmid allows for new strand synthesis?

A

the 3’-OH end

46
Q

true or false: the F plasmid is an episome. why?

A

true; because it can reversibly integrate itself onto the host chromosome

47
Q

where does integration of the F plasmid occur on the host genome?

A

insertion sequences

48
Q

when the F factor is not integrated onto the host chromosome, the cell is considered:

A

F+

49
Q

when the F factor is integrated into the host genome, the cell is considered:

A

HFr

50
Q

what does HFr stand for?

A

high frequency recombination

51
Q

true or false: conjugation cannot occur between HFr and F- strains.

A

false; it certainly can

52
Q

in conjugation between HFr and F- strains, an ____________ copy of the F factor is transferred

A

incomplete

53
Q

true or false: donor chromosomal DNA is transferred during HFr x F- mating

A

true

54
Q

what characterizes an F’ plasmid?

A
  • this is when the F factor is incorrectly excised from the host chromosome
  • happens with HFr plasmids
55
Q

what is transformation?

A

uptake of extracellular DNA by a bacterial cell

56
Q

bacterial cells that have the ability to take up DNA from the environment are:

A

competent

57
Q

for linear DNA to be stably transformed, it must:

A

integrate into the chromosome

58
Q

what is transduction?

A

the transfer of bacterial genes by viruses

59
Q

match the following:

  1. lytic cycle
  2. lysogenic cycle

a. viral DNA integrates into host genome (becoming a prophage)
b. host cell is destroyed

A

1b
2a

60
Q

what is phage mediated transduction?

A

host (bacterial) gene transfer that is facilitated by bacteriophages

61
Q

true or false: phage mediated transduction is typically an intentional process.

A

false; it’s typically accidental

62
Q

what are the two types of phage mediated transduction?

A
  • generalized transduction
  • specialized transduction
63
Q

match the following:

  1. errors in the lytic cycle
  2. errors in the lysogenic cycle

a. generalized transduction
b. specialized transduction

A

1a
2b

64
Q

true or false: in generalized transduction, any part of the bacterial genome can be transferred.

A

true (“generalized”)!

65
Q

generalized transduction occurs due to mistakenly packaged:

A

bacterial DNA into viral proteins (like the phage head)

66
Q

how much viral DNA is packaged in with bacterial DNA during generalized transduction?

A

none!

67
Q

specialized transduction occurs due to incorrect:

A

excision of the prophage from the host genome

68
Q

true or false: in specialized transduction, the new virions will receive some of the viral genome and some of the bacterial genome.

A

true!

69
Q

in specialized transduction, where does the transferred host DNA come from?

A

the host DNA surrounding the viral integration site

70
Q

true or false: mutations cannot cause antibiotic resistance.

A

false; they do, and they do so spontaneously

71
Q

what are two ways antibiotic resistance can occur?

A
  • mutations
  • horizontal gene transfer
72
Q

resistance genes can be found in what three places?

A
  • bacterial chromosomes
  • transposons
  • plasmids

Microbio 3220 (24 decks)

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