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Microbiology > Lecture 7 Bacterial Genetics > Flashcards

Lecture 7 Bacterial Genetics Flashcards

(60 cards)

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1
Q

What is direct selection?

A

cells inoculated onto medium that supports growth of MUTANT but not PARENT

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2
Q

Antibiotic resistant mutants grow on what medium?
- parents do NOT

A

Medium with antibiotics

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3
Q

What is indirect selection?

A

isolates auxotroph from prototrophic parent stain

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4
Q

Why is indirect selection difficult

A

Since the parents grow on any medium which the auxotroph can also grow on

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5
Q

________ indirectly selects auxotrophs

A

Replica plating

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6
Q

in replica plating, all cells will form on ________ agar

Auxotrophs fail to grow on ________ agar

A

Nutrients

glucose-salts

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7
Q

Colonies that are missing on ________ agar allow identification of auxotrophs on master plate

A

glucose-salts

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8
Q

Penicillin enrichment does what?

A

selectively kills prototrophs

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9
Q

penicillin enrichment increases or decreases auxotrophs before replica plating?

A

increases

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10
Q

Penicillin kills only ________ cells

A

GRowing

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11
Q

prototrophs grow in ________ medium, auxotrophs do not

A

glucose-salts

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12
Q

________ added before cells are plated on nutrient agar to create master plate

A

Penicillinase

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13
Q

Carcinogens cause many cancers, most are ________

A

mutagens

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14
Q

Mutagens increase ________ of spontaneous reversions

A

low frequence

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15
Q

________ measures effect of chemical on reversion rate of histidine requiring salmonella auxotrophs

A

Ames test

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16
Q

If chemical is mutagenic, what happens to reversion rate in relation to control?

A

increases (more colonies grow)

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17
Q

What do recombinants do?

A

acquires genes from other cells by horizontal gene transfer

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18
Q

if you combine two strands that cannot grow on glucose salts medium, what mutants would occur?

A

spontaneous mutants are unlikely, simultaneous mutations are required

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19
Q

colonies that can grow on glucose salts medium require what?

A

acquired genes from other strains

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20
Q

What is DNA mediated transformation?

A

Naked DNA taken up from environment

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21
Q

What is transduction

A

DNA is transferred from one bacteria to another by bacteriophage

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22
Q

What is conjugation

A

DNA transfer during cell to cell contact

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23
Q

What is conjugation

A

DNA transfer during cell to cell contact

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24
Q

transferred DNA replicated only if it is a________ with origin of replication

A

Replicon

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25
DNA fragments can be added to recipient chromosome by ________
Homologous recombination
26
In homologous recombination
Donor DNA replaces complementary region of recipient cell's DNA
27
What are examples of replicons?
chromosomes, plasmids
28
transformation involves uptake of ________DNA
naked
29
What is naked DNA?
DNA is not within cell or virus originates from cells that have burst or secreted addition of DNase prevents transformation
30
For DNA mediated transformation, recipient cell must be ________
Competent
31
Most cells take up DNA regardless of ________
origin
32
Some cells only accept DNA from
closely related bacteria
33
In transduction, ________ infect bacterial cells
phages
34
How does the phage transfer DNA?
attaches to cell, injects its nucleic acid phage enzymes cut bacterial DNA into small pieces bacterial cell enzymes produce phage nucleic acid and coat phage particles are released from bacteria
35
What is generalized transduction?
when a fragment of bacterial DNA enters the phage protein coat - produces transducing particle
36
Transducing particle may attach to ________ and ________
another bacterial cell, inject DNA - new DNA may be integrated into chromosome
37
What does a conjugative plasmid do?
Direct their own transfer
38
________ do not have to integrate into chromosome in conjugation
Replicons
39
In plasmid transfer for conjugation, what happens?
F pilus binds to receptor on recipient cell wall F pilus contracts, pulls cells together enzyme cuts plasmid at origin of transfer single DNA strand is transferred complementary strands synthesizes Both cells are now F
40
In chromosome transfer for conjugation, what happens?
involves Hfr cells (high frequence of recombination F plasmid is integrated into chromosome via homologous recombination process is reversible F' plasmid results when small piece of chromosome is removed with F plasmid DNA F' plasmid is replicon, transferred to F cells - carries bacterial DNA into new cells
41
What is Hfr cells?
high frequencey of recombination F plasmid is integrated into chromosome via homologous recombination
42
What is core genome
common to all strands of the species
43
What is mobile gene pool
remaining strands that are not common to all strands of species can move from one DNA molecule to another
44
What are included in the mobile gene pool?
plasmids, transposons, genomic islands, phage DNA
45
what are plasmids?
dsDNA with origin of replication circular double stranded DNA
46
What is the function plasmids?
encode nonessential information, allow survival in particular environment low-copy-number to high-copy-number
47
Plasmids have what host range?
narrow
48
Mobilizable plasmid requires _______ plasmid for transfer
Conjugative
49
What do resistant (R plasmids) plasmids
encode resistance to antimicrobial medication
50
R plasmids are conjugative plasmids with _______ host range
Broad
51
what do transposons do?
provide mechanism for moving DNA
52
Transposons can move into other _______ in the same cell
replicons
53
What does insertion sequence do
encodes only transposase enzyme, inverted repeats
54
_______ transposons include one or more genes
composite
55
Composite transposon integrate via what?
non-homologous recombination
56
What are genomic islands?
large DNA segments in genome that originated in other sepcies
57
In genomic islands, what are the nucleotides like?
very different from genome G-C base pair ratio characteristic for each species - if a large segment has a different G-C ratio, it indicates that the segment originated from a foreign source and was transferred through horizontal cell transfer
58
What are the characteristics encoded by genomic islands?
use of specific energy sources acid tolerance ability to cause disease - pathogenicity islands
59
CRISPR systems include small segments of _______ DNA that recognize the specific DNA if it invades the cell agian
phage
60
in CRISPR, what happens in the first invasion?
complex of Cas proteins cut DNA into short segments

Microbiology (16 decks)

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