Bacterial Genetics Flashcards
1
Q
Some bacteria have multiple circular chromosomes
T/F
A
T
2
Q
some bacteria have linear chromosomes
T/F
A
T
3
Q
A change in the sequence of template DNA is called _________
A
mutation
4
Q
Spontaneous mutation occurs naturally about one in every ______ to one in every _______ divisions.
A
million
billion
5
Q
Mutations can be induced at a desired region to create a suitable mutant, especially to ________
A
produce vaccines.
6
Q
Spontaneous mutations can result in emergence of antibiotic resistance in bacteria.
T/F
A
T
7
Q
The process of mutation is called ______ and the agent inducing mutation is called _______.
A
mutagenesis
mutagen
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,
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
10
Q
Radiation can also be a cause of DNA mutations.
T/F
A
T
11
Q
PLASMIDS
Usually they are (opened or closed?) (linear or circular?) molecules
A
Closed
Circular
12
Q
Plasmids multiply (dependently or independently ?) of the chromosome and are inherited regularly by the daughter cells.
A
independently
13
Q
Types of plasmids
___ factor, ____ factor, ____ and __ factor
A
R
Col
r-RTF
F
14
Q
A bacterium can have no plasmids at all
T/F
A
T
15
Q
A bacterium cant have many plasmids
T/F
A
F
They can…like 20-30
16
Q
A bacterium can have multiple copies of a plasmid.
T/F
A
T
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
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
19
Q
Plasmids carry virulence determinant genes.
T/F
A
T
20
Q
DNA repair enzymes are coded in the ________
A
plasmid
21
Q
Plasmids Code for colonization factors that is necessary for their attachment.
T/F
A
T
22
Q
Types of plasmids
F factor: ( ____ factor or____ factor)
A
fertility; sex
23
Q
Most plasmids are able to mediate their own transfer to other cells.
T/F
A
F
Unable
24
Q
F factor is a plasmid that codes for ________ for its own transfer to other cells.
A
sex pili
25
Those bacteria that possess transfer factor are called __, (____, ____ ) such bacteria have _______ on their surface.
Those cells lacking this factor are designated ____ (______, _____)
F+; male; donor
sex pili
F- ; female; recipient
26
F plasmid is transferred to other cells through _______.
conjugation
27
An F- cell will become _____. when it receives the ______ factor from an F+ cell.
F+
fertility
28
___ factor: a plasmid that codes for the transmissible drug resistance
R
29
Bacteria possessing such R plasmids are resistant to many antibiotics and this drug resistance is transferred to _____ species through _____
closely related
conjugation
30
R-factor plasmids are usually transferred to related species along with _____.
RTF
31
Transposable genetic elements are __________ that have the capacity to __________________ (i.e. ______ genes).
segments of DNA
move from one location to another
jumping
32
Transposable genetic elements
TYPES
_________
________
Insertion sequences
Transposons
33
Transposable genetic elements
TYPES
Insertion sequences
The introduction of an insertion sequence into a bacterial gene will result in _______________
the inactivation of the gene
34
Many antibiotic resistance genes are located on transposons
T/F
T
35
Transfer of genes
Genes are then transferred by :
Vertical method
_______________
Horizontal methods
—————
___________
____________
Parent to offspring
Conjugation
Transduction
Transformation
36
Transfer of genes
Horizontal methods
Conjugation (____________ transfer)
Transduction (_________ transfer)
Transformation (______ transfer)
bacteria-to-bacteria
viral-mediated
free DNA
37
Conjugation
Bacterial conjugation is the ________ from a ______ bacterium to a _____ bacterium.
transfer of DNA
living donor
recipient
38
First step in conjugation is __________
mating pair formation
39
Mating pair formation
The main structure that allows mating pair formation is the ______
sex pilus
40
Each Gram negative F+ bacterium has ______ sex pili that bind to a __________ protein on recipient bacteria to initiate mating.
1 to 3
specific outer membrane
41
Mating pair formation
The sex pilus then ____, bringing the two bacteria in contact and the two cells become _______ at a point of _______________ contact.
retracts
bound together
direct envelope-to- envelope
42
Mating pair formation
In Gram-positive bacteria ________ are produced which bring the two bacteria into contact.
sticky surface molecules
43
Mating pair formation
Gram-positive donor bacteria produce ______ that cause them to aggregate with recipient cells
adhesins
44
In gran positive mating pair formation
sex pili are involved
T/F
F
sex pili are not involved
45
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.
F+ plasmid
chromosomal DNA
46
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.
separate; enters the recipient; remains in the donor.
Complementary strands
an F+ male
47
F+ conjugation
During conjugation, cytoplasm, cell material and DNA passes from donor to recipient.
T/F
F
no cytoplasm or cell material except DNA passes from donor to recipient.
48
F+ conjugation
After conjugation, the cells ________
Following successful conjugation the recipient _______ and the donor ______
break apart.
becomes F+
remains F+.
49
Resistance plasmid conjugation:
Some Gram- _____ bacteria harbor plasmids that contain antibiotic resistance genes, such plasmids are called ____ factors.
negative
R
50
The R factor has two components, one that codes for _______ (like __ factor) called _______ and the other R determinant that contains genes coding for _________
self transfer; F
RTF (resistance transfer factor)
antibiotic resistance.
51
R plasmids may confer resistance to as many as ____ different antibiotics, and by ______ they can be rapidly disseminated through the bacterial population.
five
conjugation
52
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 _________
enters the recipient
remains in the donor.
complementary copy.
53
R-plasmid has genes coding for multiple ________ as well as ______ formation.
The recipient becomes ________ and ______ , and is now able to _______________________
antibiotic resistance
sex pilus
multiple antibiotic resistant and male
transfer R-plasmids to other bacteria.
54
R plasmids conjugation
RTF can not disassociate from the R determinant to exist as separate entities.
T/F
F
Sometimes RTF may disassociate from the R determinant and the two components may exist as separate entities.
55
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 ________________
can not transfer this resistance to other cells.
56
Sometimes RTF can have other genes attached to it apart from R determinants.
T/F
If T, give example
If F, why?
T
such as those coding for hemolysin, enterotoxin
57
Genetic recombination
Homologous DNA sequences having ________________ sequences are exchanged by means of _____ (______), and _____ of paired DNA segments
NEARLY the same nucleotide
breakage; crossing over; reunion
58
General or homologous recombination is mediated by an enzyme, _______ protein
RecA
59
Hfr conjugation
Plasmids may integrate into the bacterial chromosome by a __________ event
recombination
60
Hfr (__________________) conjugation
high frequency recombinant
61
Hfr conjugation
After integration, both plasmid and chromosome will still replicate as seperate units
T/F
F
After integration, both plasmid and chromosome will replicate as a single unit.
62
Hfr conjugation
A plasmid that is capable of integrating into the chromosome is called _________.
An episome
63
If the F plasmid is integrated into the chromosome it is called ______ cell.
an Hfr
64
In HFR conjugation
After integration, both chromosome and plasmid can be conjugally transferred to a recipient cell.
T/F
T
65
Hfr cells are called so because they are able to ___________________________
transfer chromosomal genes to recipient cells with high frequency.
66
In HFR conjugation
The bacterial connection usually breaks before the transfer of the entire chromosome is completed
T/F
T
67
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 _____________
remainder of the F+ plasmid
a part of the Hfr chromosome as well as the plasmid
receive complete F factor.
68
In HFR conjugation
After conjugation the Hfr cell ________ while the F- cell _____________
remains Hfr
does not become F+ and continues to remain F-.
69
In HFR conjugation
the transferred chromosome fragment recombines with the chromosome of F- cell thereby transferring _________\
some new property to the recipient cell
70
Significance of conjugation
Among the Gram _____ bacteria this is the major way that bacterial genes are transferred.
negative
71
Conjugation
Transfer can occur between different species of bacteria.
T/F
T
72
_______ are viruses that parasitize bacteria and use their machinery for their own replication
Bacteriophages
73
Life cycle of bacteriophage may either by _____________
lytic or lysogenic.
74
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
erroneously packaged into the bacteriophage capsid.
lysis
infects another bacterium
recombination
75
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.
phage DNA gets incorporated into the bacterium chromosome.
prophage
it were a part of bacterial chromosome.
lysogenic; lysogenic
76
In lysogenic transduction
The genes present in the phage DNA also get expressed in the bacterium.
T/F
T
77
Only those strains of Corynebacterium diphtheriae that have been lysogenised with ________ produce the _____ toxin.
beta prophage
diphtheria
78
Transformation
Transformation is gene transfer resulting from the uptake of ______ from a donor cell.
naked DNA
79
TRANSFORMATION
Certain bacteria (e.g. _____,______,______,______) can take up DNA from the environment
Bacillus, Haemophilus, Neisseria, Pneumococcus
80
TRANSFORMATION
DNA that is taken up can be incorporated into the recipient's chromosome
T/F
T
81
Transformation
DNA that is taken up can be incorporated into the recipient's chromosome
T/F
T
82
Transformation
DNA that is taken up can be incorporated into the recipient's chromosome
T/F
T
83
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 __________
dies; degraded
dead
DNA binding proteins ; cell wall ; living
Nuclease; destroyed; penetrates the recipient bacterium.
84
The ______ protein promotes genetic exchange (recombination) between a fragment of the donor's DNA and the recipient's DNA
Rec A
85
Genetic mechanisms of drug resistance
___________
_____________
Mutations
Transferable drug resistance
