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Medical Microbiology > L9: Genetic Aspect of Pathogenicity > Flashcards

L9: Genetic Aspect of Pathogenicity Flashcards

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1
Q

In transcription, RNAP binds to the ____
A. inducer
B. promoter
C. start site
D. end site

A

B. promoter

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2
Q

True or False: Translation is accomplished by ribosomes with the help of tRNA

A

True

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3
Q

Why is it that translation of mRNA can begin as soon as its transcription starts in pathogens?

A

Because bacteria lack nuclear membrane - therefore transcription/translation take place in the same spot!

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4
Q

True or False: Bacteria are poylcistronic

A

True (one mRNA encodes many proteins!)

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5
Q

In gene transcription, ribosome attaches the binding site (Shine-Dalgarno) of mRNA chain and moves along as mRNA synthesis occurs. However, degradation of mRNA follows shortly after translation. Why is this?

A

mRNAs highly unstable

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6
Q

Several ribosomes can translate an mRNA at the same time, forming what is called a ____

A

polysome

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7
Q

____: the organization of tandem genes in transcriptional units

A

operon

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8
Q

True or False: The operon speeds and coordinates bacterial response

A

True

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9
Q

_____: serves as control site, is where products from pathway can bind and repress synthesis of the operon
A. promoter
B. operator
C. inducer

A

B. operator

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10
Q

Where does RNAP bind to begin transcription?
A. promoter
B. operator
C. inducer

A

A. promoter

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11
Q

What is found at 5’ end of bacteria mRNA?
3’ end?

A

5’ = triphosphate
3’ = last base of mRNA

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12
Q

True or False: In bacterial mRNA, there is a coding region and non-coding region, which are additional sequences on either end (leader and trailer) and between coding region (intercistronic)

A

True

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13
Q

In bacterial transcription, _____ Factor binds to RNAP

A

Sigma Factor

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14
Q

True or False: The Sigma Factor has catalytic activity and helps core enzyme recognize promoter

A

False - while the sigma factors does help core enzyme to recognize promoter, it LACKS catalytic activity

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15
Q

When does the sigma factor fall off?

A

Once RNAP holoenzyme has bound and transcription is initiated

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16
Q

True or False: Most bacteria can only synthesize one sigma factor

A

False - most bacteria can make several sigma factors, each of which recognize a different promoter sequence

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17
Q

The ___ operon is an example of inducible gene transcription

A

lac operon

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18
Q

Why is the default mode of the lac operon ‘off’ (no transcription)?

A

Active repressor binds at operator site, which interferes with RNAP binding

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19
Q

When an inducer molecule binds to the repressor, there is a conformation change in the ___

A

repressor

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20
Q

What type of repressor is NOT able to bind to operator site, leads to transcription activation!
A. Inactive repressor
B. Active repressor

A

A. Inactive repressor

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21
Q

In the lac operon, when glucose is present:
a. is there any inducer?
b. is lac mRNA made?

A

a. no inducer
b. no lac mRNA made
- repressor binds to operator, prevents RNAP from transcribing operon

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22
Q

What three proteins are the result of turning the lac operon on?

A

Permease
Transacetylase
B-galactosidase

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23
Q

___ is the inducer of the lac operon when lactose is present. In particular, it binds to repressor mRNA

A

Allolactose

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24
Q

True or False: In the lac operon, activator proteins bind to specific sequences adjacent to the promoter site of regulated genes

A

True

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25
Which molecule allows for positive regulation of lac operon? A. cAMP B. ATP C. AMP D. CTP
A. cAMP
26
In the presence of lactose (no glucose) the lac operon will increase ____ and ____
cAMP and transcription
27
cAMP binds to ____, a transcription activator protein, which activates transcription of galactosidase structural genes
CRP
28
For the lac operon to have high transcription, lactose is converted into an effector, which is known as _____. ___ binds to lac ____ and inactivates it, so it cannot bind to the operator
allolactose; allolactose ; lac repressor
29
For the lac operon to have high levels of transcription, activator molecules (CRP/CAP) have to be activated by _____, then the complex binds to the promoter to turn on transcription
cAMP
30
Why is the default mode of the trp operon "ON"?
Native repressor has NO affinity for the operator site of regulated genes
31
In the repression of gene transcription, binding of co-repressor results in ACTIVATION of ____ activity and REPRESSION of _____ ____
repressor; gene transcription
32
True or False: When gene transcription is repressed, end-products of some metabolic pathways could act as co-repressors
True
33
The trp operon is an example of repressible operon
True
34
In the trp operon, there is _____ inhibition
end product
35
Which signal transduction system allows for sensing changes in the environment?
Two component signal transduction
36
What are a few of the cellular functions that the two component signal transduction system is involved in?
1. Chemotaxis 2. Quorum sensing
37
The two component signal transduction detects an external signal and directs the organism to make a response that is ___ to survival
conducive
38
____: proteins that help RNAP bind to promoter
Transcription Factors/Activators (cAMP)
39
What are the two components that make up the two component signal transduction?
1. Sensor Protein: Embedded in the bacterial membrane, this protein senses physiological conditions of bacterial cell 2. Response Regulator: Binds to promoter region of gene to activate or repress
40
The sensor molecule of the two component signal transduction system generally contains a ___ kinase that autophosphorylates upon interaction with signal molecule
histidine
41
True or False: Many operons and regulons are controlled by two component regulatory systems
True
42
_____: The exchange of homologous region between two DNA molecules
Homologous Recombination
43
In bacteria, gene rearrangements are classified into which two groups?
1. Accidental DNA rearrangements 2. Programmed DNA rearrangements
44
______ rearrangements: derived from abundance of events at chromosome (e.g repair, mutation, transpositions, insertion/excision of plasmids, phages, or foreign DNA, horizontal gene transfer) A. Accidental DNA Rearrangements B. Programmed DNA Rearrangements
A. Accidental DNA Rearrangements
45
_____ rearrangements: part of genetic program, the outcome is largely predictable (e.g amplification or deletion of genes, assembly of genes from gene segments) A. Accidental DNA Rearrangements B. Programmed DNA Rearrangements
B. Programmed DNA Rearrangements
46
_______: the exchange of non-homologous but specific pieces of DNA that mediated by proteins/enzymes (site specific recombinases) that recognize specific sequences
Site specific recombination
47
Programmed DNA rearrangements consist of the movement of a gene from a ___ storage site where the gene is not expressed to an ___ site where transcription and translation occur
silent; active
48
True or False: Many silent genes encode variants of the antigens by insertion of new gene into expression locus
True
49
True or False: Programmed DNA Rearrangements are a source of consistent antigenic variation
True
50
Expression of ___ gene, gene responsible for synthesis of exotoxin in streptolysin, is an example of programmed DNA rearrangment
slo
51
True or False: In addition to providing a means of avoiding immune defenses, antigenic/phase variation may contribute to dissemination of bacteria within colonized host
True
52
_____: Switching the expression of some components from on to off _____: Alters antigenic nature of components
Phase Variation Antigenic Variation
53
True or False: DNA Inversion and Slipped Strand Mispairing are examples of Phase Variation
True
54
DNA Recombination and Point mutations are examples of which type of variation? A. Phase Variation B. Antigenic Variation
B. Antigenic Variation
55
_____ is a type of phase variation; by site specific recombination, it is a common means by which bacteria control the expression of genes located within or adjacent to the invertible region A. DNA Recombination B. Point Mutations C. Slipped Strand Mispairing D. DNA Inversions
D. DNA Inversions
56
E. coli Type 1 Fimbrae are an example of ______ A. DNA Recombination B. Point Mutations C. Slipped Strand Mispairing D. DNA Inversions
D. DNA Inversions
57
During DNA replication, mispairing occurs, leading to strand slippage and results in ___ or ____, which can lead to frame shift mutation and premature termination of protein product. This best described which type of phase variation?
insertion/deletion - Slipped Strand Mispairing
58
Opa genes involves in adhesion and invasion of N. gonorrohae and N. meningitis are examples of: A. Slipped-strand mispairings B. DNA Inversion C. Point Mutations D. DNA Recombination
A. Slipped-strand mispairings
59
True or False: Opa genes are subject for both phase and antigenic variation
True
60
Which type of antigenic variation uses homologous recombination to shuffle antigenic makeup? A. DNA Recombination B. Point Mutations
A. DNA Recombination
61
Type IV pilus of N. gonnorhoeae and capsule of S. pneumoniae use which type of antigenic variation?
DNA recombination
62
____: Simple mutations within the reading frame of genes encoding surface components, can give rise to antigenic variants no longer recognized by host immune system
Point mutations
63
Which type of antigenic variation is used by HIV, Influenza A, and M protein in S. pyrogenes?
Point mutation

Medical Microbiology (31 decks)

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