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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
what is transposition?
small segments of DNA moving about the genome (they are sometimes called jumping genes)
26
who discovered transposable elements?
Barbara McClintock in 1940s
27
what are the simplest transposable elements?
insertion sequences (IS)
28
what are composite transposons (Tn)?
transposable elements containing "extra" genes flanked by two insertion sequences
29
what are unit transposons?
- 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
what are inverted repeats? what do they mark?
- short stretches of identical nucleotides in opposite orientations - marks the ends of the IS or Tn
31
what is transposase?
an enzyme responsible for site specific transposition
32
what are direct repeats?
- host DNA that is the site for insertion - duplicated during insertion
33
what are the two types of transposition?
- simple transposition (cut and paste) - replicative transposition (copy and paste)
34
what are retrotransposons?
RNA copy of the transposable element is made and is transcribed back into DNA to integrate at the new site
35
what are plasmids?
- 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
true or false: cells cannot have more than one plasmid.
false
37
what are episomes?
plasmids that can integrate reversibly into the host chromosome
38
what are conjugative plasmids?
plasmids that can transfer copies of themselves to other bacteria during conjugation
39
true or false: plasmids can exist independently of the host chromosome.
true
40
what structure facilitates conjugation?
sex pilus/F pilus
41
true of false: donor chromosomal genes are usually transferred during conjugation.
false; they aren't (usually)
42
plasmids are replicated via what method?
rolling circle method
43
at the end of successful F+ x F- mating, what types of cells are present at the end?
two F+ cells
44
what is the synthesis of the complementary strand in rolling circle replication similar to?
similar to lagging strand synthesis
45
in the rolling circle method, which end of the nicked plasmid allows for new strand synthesis?
the 3'-OH end
46
true or false: the F plasmid is an episome. why?
true; because it can reversibly integrate itself onto the host chromosome
47
where does integration of the F plasmid occur on the host genome?
insertion sequences
48
when the F factor is not integrated onto the host chromosome, the cell is considered:
F+
49
when the F factor is integrated into the host genome, the cell is considered:
HFr
50
what does HFr stand for?
high frequency recombination
51
true or false: conjugation cannot occur between HFr and F- strains.
false; it certainly can
52
in conjugation between HFr and F- strains, an ____________ copy of the F factor is transferred
incomplete
53
true or false: donor chromosomal DNA is transferred during HFr x F- mating
true
54
what characterizes an F' plasmid?
- this is when the F factor is incorrectly excised from the host chromosome - happens with HFr plasmids
55
what is transformation?
uptake of extracellular DNA by a bacterial cell
56
bacterial cells that have the ability to take up DNA from the environment are:
competent
57
for linear DNA to be stably transformed, it must:
integrate into the chromosome
58
what is transduction?
the transfer of bacterial genes by viruses
59
match the following: 1. lytic cycle 2. lysogenic cycle a. viral DNA integrates into host genome (becoming a prophage) b. host cell is destroyed
1b 2a
60
what is phage mediated transduction?
host (bacterial) gene transfer that is facilitated by bacteriophages
61
true or false: phage mediated transduction is typically an intentional process.
false; it's typically accidental
62
what are the two types of phage mediated transduction?
- generalized transduction - specialized transduction
63
match the following: 1. errors in the lytic cycle 2. errors in the lysogenic cycle a. generalized transduction b. specialized transduction
1a 2b
64
true or false: in generalized transduction, any part of the bacterial genome can be transferred.
true ("generalized")!
65
generalized transduction occurs due to mistakenly packaged:
bacterial DNA into viral proteins (like the phage head)
66
how much viral DNA is packaged in with bacterial DNA during generalized transduction?
none!
67
specialized transduction occurs due to incorrect:
excision of the prophage from the host genome
68
true or false: in specialized transduction, the new virions will receive some of the viral genome and some of the bacterial genome.
true!
69
in specialized transduction, where does the transferred host DNA come from?
the host DNA surrounding the viral integration site
70
true or false: mutations cannot cause antibiotic resistance.
false; they do, and they do so spontaneously
71
what are two ways antibiotic resistance can occur?
- mutations - horizontal gene transfer
72
resistance genes can be found in what three places?
- bacterial chromosomes - transposons - plasmids

Microbio 3220 (24 decks)

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