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Microbiology > Lecture 7 Bacterial Genetics > Flashcards

Lecture 7 Bacterial Genetics Flashcards

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
Q

DNA fragments can be added to recipient chromosome by ________

A

Homologous recombination

26
Q

In homologous recombination

A

Donor DNA replaces complementary region of recipient cell’s DNA

27
Q

What are examples of replicons?

A

chromosomes, plasmids

28
Q

transformation involves uptake of ________DNA

A

naked

29
Q

What is naked DNA?

A

DNA is not within cell or virus
originates from cells that have burst or secreted
addition of DNase prevents transformation

30
Q

For DNA mediated transformation, recipient cell must be ________

A

Competent

31
Q

Most cells take up DNA regardless of ________

A

origin

32
Q

Some cells only accept DNA from

A

closely related bacteria

33
Q

In transduction, ________ infect bacterial cells

A

phages

34
Q

How does the phage transfer DNA?

A

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
Q

What is generalized transduction?

A

when a fragment of bacterial DNA enters the phage protein coat
- produces transducing particle

36
Q

Transducing particle may attach to ________ and ________

A

another bacterial cell, inject DNA
- new DNA may be integrated into chromosome

37
Q

What does a conjugative plasmid do?

A

Direct their own transfer

38
Q

________ do not have to integrate into chromosome in conjugation

A

Replicons

39
Q

In plasmid transfer for conjugation, what happens?

A

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
Q

In chromosome transfer for conjugation, what happens?

A

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
Q

What is Hfr cells?

A

high frequencey of recombination

F plasmid is integrated into chromosome via homologous recombination

42
Q

What is core genome

A

common to all strands of the species

43
Q

What is mobile gene pool

A

remaining strands that are not common to all strands of species

can move from one DNA molecule to another

44
Q

What are included in the mobile gene pool?

A

plasmids, transposons, genomic islands, phage DNA

45
Q

what are plasmids?

A

dsDNA with origin of replication

circular double stranded DNA

46
Q

What is the function plasmids?

A

encode nonessential information, allow survival in particular environment

low-copy-number to high-copy-number

47
Q

Plasmids have what host range?

A

narrow

48
Q

Mobilizable plasmid requires _______ plasmid for transfer

A

Conjugative

49
Q

What do resistant (R plasmids) plasmids

A

encode resistance to antimicrobial medication

50
Q

R plasmids are conjugative plasmids with _______ host range

A

Broad

51
Q

what do transposons do?

A

provide mechanism for moving DNA

52
Q

Transposons can move into other _______ in the same cell

A

replicons

53
Q

What does insertion sequence do

A

encodes only transposase enzyme, inverted repeats

54
Q

_______ transposons include one or more genes

A

composite

55
Q

Composite transposon integrate via what?

A

non-homologous recombination

56
Q

What are genomic islands?

A

large DNA segments in genome that originated in other sepcies

57
Q

In genomic islands, what are the nucleotides like?

A

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
Q

What are the characteristics encoded by genomic islands?

A

use of specific energy sources
acid tolerance
ability to cause disease
- pathogenicity islands

59
Q

CRISPR systems include small segments of _______ DNA that recognize the specific DNA if it invades the cell agian

A

phage

60
Q

in CRISPR, what happens in the first invasion?

A

complex of Cas proteins cut DNA into short segments

Microbiology (16 decks)

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