Bacterial Genetics Flashcards
Some bacteria have multiple circular chromosomes
T/F
T
some bacteria have linear chromosomes
T/F
T
A change in the sequence of template DNA is called _________
mutation
Spontaneous mutation occurs naturally about one in every ______ to one in every _______ divisions.
million
billion
Mutations can be induced at a desired region to create a suitable mutant, especially to ________
produce vaccines.
Spontaneous mutations can result in emergence of antibiotic resistance in bacteria.
T/F
T
The process of mutation is called ______ and the agent inducing mutation is called _______.
mutagenesis
mutagen
Mutagens can be chemicals
_____ acid, which alters ____ to pair with _____ instead of ______.
______ dyes, are _____ analogs that are similar in structure to ________
Nitrous; adenine; cytosine; thymine
acridine; nucleoside
nitrogenous bases,
High energy light waves such as X-rays, gamma rays, and ultraviolet light have been shown to damage DNA.
T/F
T
Radiation can also be a cause of DNA mutations.
T/F
T
PLASMIDS
Usually they are (opened or closed?) (linear or circular?) molecules
Closed
Circular
Plasmids multiply (dependently or independently ?) of the chromosome and are inherited regularly by the daughter cells.
independently
Types of plasmids
___ factor, ____ factor, ____ and __ factor
R
Col
r-RTF
F
A bacterium can have no plasmids at all
T/F
T
A bacterium cant have many plasmids
T/F
F
They can…like 20-30
A bacterium can have multiple copies of a plasmid.
T/F
T
Significance of plasmids
Code for resistance to several antibiotics especially in Gram- ______bacteria
Code for the production of________.
Code for the production of _______
negative
bacteriocines
toxins
Significance of plasmids
Code for the production of toxins (such as _______ by Escherichia coli, Vibrio cholerae, _______ toxin by Staphylococcus aureus and ____- of Clostridium tetani).
Enterotoxins
exfoliative
neurotoxin
Plasmids carry virulence determinant genes.
T/F
T
DNA repair enzymes are coded in the ________
plasmid
Plasmids Code for colonization factors that is necessary for their attachment.
T/F
T
Types of plasmids
F factor: ( ____ factor or____ factor)
fertility; sex
Most plasmids are able to mediate their own transfer to other cells.
T/F
F
Unable
F factor is a plasmid that codes for ________ for its own transfer to other cells.
sex pili
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
F plasmid is transferred to other cells through _______.
conjugation
An F- cell will become _____. when it receives the ______ factor from an F+ cell.
F+
fertility
___ factor: a plasmid that codes for the transmissible drug resistance
R
Bacteria possessing such R plasmids are resistant to many antibiotics and this drug resistance is transferred to _____ species through _____
closely related
conjugation
R-factor plasmids are usually transferred to related species along with _____.
RTF
Transposable genetic elements are __________ that have the capacity to __________________ (i.e. ______ genes).
segments of DNA
move from one location to another
jumping
Transposable genetic elements
TYPES
_________
________
Insertion sequences
Transposons
Transposable genetic elements
TYPES
Insertion sequences
The introduction of an insertion sequence into a bacterial gene will result in _______________
the inactivation of the gene
Many antibiotic resistance genes are located on transposons
T/F
T
Transfer of genes
Genes are then transferred by :
Vertical method
_______________
Horizontal methods
—————
___________
____________
Parent to offspring
Conjugation
Transduction
Transformation
Transfer of genes
Horizontal methods
Conjugation (____________ transfer)
Transduction (_________ transfer)
Transformation (______ transfer)
bacteria-to-bacteria
viral-mediated
free DNA
Conjugation
Bacterial conjugation is the ________ from a ______ bacterium to a _____ bacterium.
transfer of DNA
living donor
recipient
First step in conjugation is __________
mating pair formation
Mating pair formation
The main structure that allows mating pair formation is the ______
sex pilus
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
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
Mating pair formation
In Gram-positive bacteria ________ are produced which bring the two bacteria into contact.
sticky surface molecules
Mating pair formation
Gram-positive donor bacteria produce ______ that cause them to aggregate with recipient cells
adhesins
In gran positive mating pair formation
sex pili are involved
T/F
F
sex pili are not involved
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
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
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.
F+ conjugation
After conjugation, the cells ________
Following successful conjugation the recipient _______ and the donor ______
break apart.
becomes F+
remains F+.
Resistance plasmid conjugation:
Some Gram- _____ bacteria harbor plasmids that contain antibiotic resistance genes, such plasmids are called ____ factors.
negative
R
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.
R plasmids may confer resistance to as many as ____ different antibiotics, and by ______ they can be rapidly disseminated through the bacterial population.
five
conjugation
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.
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.
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.
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.
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
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
General or homologous recombination is mediated by an enzyme, _______ protein
RecA
Hfr conjugation
Plasmids may integrate into the bacterial chromosome by a __________ event
recombination
Hfr (__________________) conjugation
high frequency recombinant
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.
Hfr conjugation
A plasmid that is capable of integrating into the chromosome is called _________.
An episome
If the F plasmid is integrated into the chromosome it is called ______ cell.
an Hfr
In HFR conjugation
After integration, both chromosome and plasmid can be conjugally transferred to a recipient cell.
T/F
T
Hfr cells are called so because they are able to ___________________________
transfer chromosomal genes to recipient cells with high frequency.
In HFR conjugation
The bacterial connection usually breaks before the transfer of the entire chromosome is completed
T/F
T
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.
In HFR conjugation
After conjugation the Hfr cell ________ while the F- cell _____________
remains Hfr
does not become F+ and continues to remain F-.
In HFR conjugation
the transferred chromosome fragment recombines with the chromosome of F- cell thereby transferring _________\
some new property to the recipient cell
Significance of conjugation
Among the Gram _____ bacteria this is the major way that bacterial genes are transferred.
negative
Conjugation
Transfer can occur between different species of bacteria.
T/F
T
_______ are viruses that parasitize bacteria and use their machinery for their own replication
Bacteriophages
Life cycle of bacteriophage may either by _____________
lytic or lysogenic.
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
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
In lysogenic transduction
The genes present in the phage DNA also get expressed in the bacterium.
T/F
T
Only those strains of Corynebacterium diphtheriae that have been lysogenised with ________ produce the _____ toxin.
beta prophage
diphtheria
Transformation
Transformation is gene transfer resulting from the uptake of ______ from a donor cell.
naked DNA
TRANSFORMATION
Certain bacteria (e.g. _____,______,______,______) can take up DNA from the environment
Bacillus, Haemophilus, Neisseria, Pneumococcus
TRANSFORMATION
DNA that is taken up can be incorporated into the recipient’s chromosome
T/F
T
Transformation
DNA that is taken up can be incorporated into the recipient’s chromosome
T/F
T
Transformation
DNA that is taken up can be incorporated into the recipient’s chromosome
T/F
T
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.
The ______ protein promotes genetic exchange (recombination) between a fragment of the donor’s DNA and the recipient’s DNA
Rec A
Genetic mechanisms of drug resistance
___________
_____________
Mutations
Transferable drug resistance
