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House Microbiology > Bacterial Genetics > Flashcards

Bacterial Genetics Flashcards

1
Q

Some bacteria have multiple circular chromosomes

T/F

A

T

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2
Q

some bacteria have linear chromosomes

T/F

A

T

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3
Q

— A change in the sequence of template DNA is called _________

A

mutation

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4
Q

Spontaneous mutation occurs naturally about one in every ______ to one in every _______ divisions.

A

million

billion

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5
Q

Mutations can be induced at a desired region to create a suitable mutant, especially to ________

A

produce vaccines.

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6
Q

Spontaneous mutations can result in emergence of antibiotic resistance in bacteria.

T/F

A

T

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7
Q

The process of mutation is called ______ and the agent inducing mutation is called _______.

A

mutagenesis

mutagen

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8
Q

Mutagens can be chemicals

_____ acid, which alters ____ to pair with _____ instead of ______.

______ dyes, are _____ analogs that are similar in structure to ________

A

Nitrous; adenine; cytosine; thymine

acridine; nucleoside

nitrogenous bases,

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9
Q

High energy light waves such as X-rays, gamma rays, and ultraviolet light have been shown to damage DNA.

T/F

—

A

T

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10
Q

Radiation can also be a cause of DNA mutations.

T/F

A

T

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11
Q

PLASMIDS

—
—Usually they are (opened or closed?) (linear or circular?) molecules

A

Closed
Circular

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12
Q

Plasmids multiply (dependently or independently ?) of the chromosome and are inherited regularly by the daughter cells.

A

independently

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13
Q

Types of plasmids
___ factor, ____ factor, ____ and __ factor

A

R
Col
r-RTF
F

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14
Q

A bacterium can have no plasmids at all

T/F

A

T

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15
Q

A bacterium cant have many plasmids

T/F

A

F

They can…like 20-30

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16
Q

A bacterium can have multiple copies of a plasmid.

T/F

A

T

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17
Q

Significance of plasmids
—
Code for resistance to several antibiotics especially in Gram- ______bacteria
—
Code for the production of________.
— Code for the production of _______

A

negative

bacteriocines

toxins

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18
Q

Significance of plasmids
—

— Code for the production of toxins (such as _______ by Escherichia coli, Vibrio cholerae, _______ toxin by Staphylococcus aureus and ____- of Clostridium tetani).

A

Enterotoxins

exfoliative

neurotoxin

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19
Q

Plasmids carry virulence determinant genes.

T/F

A

T

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20
Q

DNA repair enzymes are coded in the ________

A

plasmid

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21
Q

Plasmids Code for colonization factors that is necessary for their attachment.

T/F

A

T

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22
Q

Types of plasmids

F factor: ( ____ factor or____ factor)

A

fertility; sex

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23
Q

Most plasmids are able to mediate their own transfer to other cells.

T/F

A

F

Unable

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24
Q

F factor is a plasmid that codes for ________ for its own transfer to other cells.

A

sex pili

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25
Q

Those bacteria that possess transfer factor are called __, (____, ____ ) such bacteria have _______ on their surface.

Those cells lacking this factor are designated ____ (______, _____)

A

F+; male; donor

sex pili

F- ; female; recipient

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26
Q

F plasmid is transferred to other cells through _______.

A

conjugation

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27
Q

An F- cell will become _____. when it receives the ______ factor from an F+ cell.

A

F+

fertility

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28
Q

___ factor: a plasmid that codes for the transmissible drug resistance
—

A

R

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29
Q

— Bacteria possessing such R plasmids are resistant to many antibiotics and this drug resistance is transferred to _____ species through _____
—

A

closely related

conjugation

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30
Q

R-factor plasmids are usually transferred to related species along with _____.

A

RTF

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31
Q

Transposable genetic elements are __________ that have the capacity to __________________ (i.e. ______ genes).
—

A

segments of DNA

move from one location to another

jumping

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32
Q

Transposable genetic elements

— TYPES
—
_________

________
—

A

Insertion sequences
—
— Transposons

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33
Q

Transposable genetic elements

— TYPES
— Insertion sequences
— The introduction of an insertion sequence into a bacterial gene will result in _______________
—

A

the inactivation of the gene

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34
Q

— Many antibiotic resistance genes are located on transposons

T/F

A

T

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35
Q

Transfer of genes

Genes are then transferred by :

Vertical method
_______________

Horizontal methods
—————
___________
____________

A

Parent to offspring

Conjugation
Transduction
Transformation

36
Q

Transfer of genes

Horizontal methods
Conjugation (____________ transfer)
Transduction (_________ transfer)
Transformation (______ transfer)

A

bacteria-to-bacteria

viral-mediated

free DNA

37
Q

Conjugation
Bacterial conjugation is the ________ from a ______ bacterium to a _____ bacterium.

A

transfer of DNA

living donor

recipient

38
Q

First step in conjugation is __________

A

mating pair formation

39
Q

Mating pair formation
— The main structure that allows mating pair formation is the ______

A

sex pilus

40
Q

— Each Gram negative F+ bacterium has ______ sex pili that bind to a __________ protein on recipient bacteria to initiate mating.
—

A

1 to 3

specific outer membrane

41
Q

Mating pair formation

The sex pilus then ____, bringing the two bacteria in contact and the two cells become _______ at a point of _______________ contact.
—

A

retracts

bound together

direct envelope-to- envelope

42
Q

Mating pair formation

— In Gram-positive bacteria ________ are produced which bring the two bacteria into contact.
—

A

sticky surface molecules

43
Q

Mating pair formation

Gram-positive donor bacteria produce ______ that cause them to aggregate with recipient cells

A

adhesins

44
Q

In gran positive mating pair formation

sex pili are involved

T/F

A

F

sex pili are not involved

45
Q

F+ conjugation
This results in the transfer of an _________ (coding only for a sex pilus) but not ___________ from a male donor bacterium to a female recipient bacterium.

A

F+ plasmid

chromosomal DNA

46
Q

F+ conjugation

The two strands of the plasmid _________.

One strand ________ while one strand ________

__________ are synthesized in both donor and recipient cells.

The recipient then becomes _____ and can make a sex pilus.

A

separate; enters the recipient; remains in the donor.

Complementary strands

an F+ male

47
Q

F+ conjugation

During conjugation, cytoplasm, cell material and DNA passes from donor to recipient.

T/F

A

F

no cytoplasm or cell material except DNA passes from donor to recipient.

48
Q

F+ conjugation

After conjugation, the cells ________

Following successful conjugation the recipient _______ and the donor ______

A

break apart.

becomes F+

remains F+.

49
Q

Resistance plasmid conjugation:

Some Gram- _____ bacteria harbor plasmids that contain antibiotic resistance genes, such plasmids are called ____ factors.

A

negative

R

50
Q

The R factor has two components, one that codes for _______ (like __ factor) called _______ and the other R determinant that contains genes coding for _________

A

self transfer; F

RTF (resistance transfer factor)

antibiotic resistance.

51
Q

R plasmids may confer resistance to as many as ____ different antibiotics, and by ______ they can be rapidly disseminated through the bacterial population.

A

five

conjugation

52
Q

R plasmids conjugation

During conjugation there is transfer of resistance plasmid (Rplasmid) from a donor bacterium to a recipient.
One plasmid strand ______ bacterium while one strand _______
Each strand then makes a _________

A

enters the recipient

remains in the donor.

complementary copy.

53
Q

R-plasmid has genes coding for multiple ________ as well as ______ formation.

The recipient becomes ________ and ______ , and is now able to _______________________

A

antibiotic resistance

sex pilus

multiple antibiotic resistant and male

transfer R-plasmids to other bacteria.

54
Q

R plasmids conjugation

RTF can not disassociate from the R determinant to exist as separate entities.

T/F

A

F

Sometimes RTF may disassociate from the R determinant and the two components may exist as separate entities.

55
Q

R plasmids conjugation

Sometimes RTF may disassociate from the R determinant and the two components may exist as separate entities.
In such cases though the host cell remains resistant to antibiotics, but it ________________

A

can not transfer this resistance to other cells.

56
Q

Sometimes RTF can have other genes attached to it apart from R determinants.

T/F

If T, give example
If F, why?

A

T

such as those coding for hemolysin, enterotoxin

57
Q

Genetic recombination
—
Homologous DNA sequences having ________________ sequences are exchanged by means of _____ (______), and _____ of paired DNA segments
—

A

NEARLY the same nucleotide

breakage; crossing over; reunion

58
Q

General or homologous recombination is mediated by an enzyme, _______ protein

A

RecA

59
Q

Hfr conjugation

Plasmids may integrate into the bacterial chromosome by a __________ event

A

recombination

60
Q

Hfr (__________________) conjugation

A

high frequency recombinant

61
Q

Hfr conjugation

After integration, both plasmid and chromosome will still replicate as seperate units

T/F

A

F

After integration, both plasmid and chromosome will replicate as a single unit.

62
Q

Hfr conjugation

A plasmid that is capable of integrating into the chromosome is called _________.

A

An episome

63
Q

If the F plasmid is integrated into the chromosome it is called ______ cell.

A

an Hfr

64
Q

In HFR conjugation

After integration, both chromosome and plasmid can be conjugally transferred to a recipient cell.

T/F

A

T

65
Q

Hfr cells are called so because they are able to ___________________________

A

transfer chromosomal genes to recipient cells with high frequency.

66
Q

In HFR conjugation

The bacterial connection usually breaks before the transfer of the entire chromosome is completed

T/F

A

T

67
Q

In HFR conjugation

The bacterial connection usually breaks before the transfer of the entire chromosome is completed so the _____________ rarely enters the recipient.
—
Usually only _______________ is transferred during conjugation and the recipient cell does not _____________

A

remainder of the F+ plasmid

a part of the Hfr chromosome as well as the plasmid

receive complete F factor.

68
Q

In HFR conjugation

After conjugation the Hfr cell ________ while the F- cell _____________

—

A

remains Hfr

does not become F+ and continues to remain F-.

69
Q

In HFR conjugation

the transferred chromosome fragment recombines with the chromosome of F- cell thereby transferring _________\

A

some new property to the recipient cell

70
Q

Significance of conjugation

Among the Gram _____ bacteria this is the major way that bacterial genes are transferred.

A

negative

71
Q

Conjugation

Transfer can occur between different species of bacteria.

T/F

A

T

72
Q

_______ are viruses that parasitize bacteria and use their machinery for their own replication

A

Bacteriophages

73
Q

Life cycle of bacteriophage may either by _____________

A

lytic or lysogenic.

74
Q

Lytic Transduction

In the lytic type of bacteriophages, when the phages replicate inside the host bacteria the bacterial chromosome is _______________

— They are released with _______ of bacterium
— The bacteriophage then __________
—
The donor bacterium’s DNA is exchanged by _______ for some of the recipient’s DNA

A

erroneously packaged into the bacteriophage capsid.

lysis

infects another bacterium

recombination

75
Q

Lysogenic transduction

In case of lysogenic cycle, the ___________

This is called a _________ and it behaves as if ___________
This process is known as ______ conversion and the bacteria are called _________ bacteria.

A

phage DNA gets incorporated into the bacterium chromosome.

prophage

it were a part of bacterial chromosome.

lysogenic; lysogenic

76
Q

In lysogenic transduction

The genes present in the phage DNA also get expressed in the bacterium.

T/F

A

T

77
Q

Only those strains of Corynebacterium diphtheriae that have been lysogenised with ________ produce the _____ toxin.

A

beta prophage

diphtheria

78
Q

Transformation

Transformation is gene transfer resulting from the uptake of ______ from a donor cell.

A

naked DNA

79
Q

TRANSFORMATION

Certain bacteria (e.g. _____,______,______,______) can take up DNA from the environment

A

Bacillus, Haemophilus, Neisseria, Pneumococcus

80
Q

TRANSFORMATION

DNA that is taken up can be incorporated into the recipient’s chromosome

T/F

A

T

81
Q

Transformation

DNA that is taken up can be incorporated into the recipient’s chromosome

T/F

A

T

82
Q

Transformation

DNA that is taken up can be incorporated into the recipient’s chromosome

T/F

A

T

83
Q

Steps in transformation

A bacterium ____ and is _____.

A fragment of DNA from the ____ donor bacterium binds to ________ on the ____ of a ____ recipient bacterium.

_______ enzymes then cut the bound DNA into fragments.

One strand is _____ and the other __________

A

dies; degraded

dead

DNA binding proteins ; cell wall ; living

Nuclease; destroyed; penetrates the recipient bacterium.

84
Q

The ______ protein promotes genetic exchange (recombination) between a fragment of the donor’s DNA and the recipient’s DNA

A

Rec A

85
Q

Genetic mechanisms of drug resistance

___________
_____________

A

Mutations
Transferable drug resistance

House Microbiology (93 decks)

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