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Medical Microbiology > L9: Genetic Aspect of Pathogenicity > Flashcards

L9: Genetic Aspect of Pathogenicity Flashcards

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Biology 101 flashcards USMLE® Step 1 flashcards
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
Q

Which molecule allows for positive regulation of lac operon?
A. cAMP
B. ATP
C. AMP
D. CTP

A

A. cAMP

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26
Q

In the presence of lactose (no glucose) the lac operon will increase ____ and ____

A

cAMP and transcription

27
Q

cAMP binds to ____, a transcription activator protein, which activates transcription of galactosidase structural genes

A

CRP

28
Q

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

A

allolactose; allolactose ; lac repressor

29
Q

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

A

cAMP

30
Q

Why is the default mode of the trp operon “ON”?

A

Native repressor has NO affinity for the operator site of regulated genes

31
Q

In the repression of gene transcription, binding of co-repressor results in ACTIVATION of ____ activity and REPRESSION of _____ ____

A

repressor; gene transcription

32
Q

True or False: When gene transcription is repressed, end-products of some metabolic pathways could act as co-repressors

A

True

33
Q

The trp operon is an example of repressible operon

A

True

34
Q

In the trp operon, there is _____ inhibition

A

end product

35
Q

Which signal transduction system allows for sensing changes in the environment?

A

Two component signal transduction

36
Q

What are a few of the cellular functions that the two component signal transduction system is involved in?

A
  1. Chemotaxis
  2. Quorum sensing
37
Q

The two component signal transduction detects an external signal and directs the organism to make a response that is ___ to survival

A

conducive

38
Q

____: proteins that help RNAP bind to promoter

A

Transcription Factors/Activators (cAMP)

39
Q

What are the two components that make up the two component signal transduction?

A
  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
Q

The sensor molecule of the two component signal transduction system generally contains a ___ kinase that autophosphorylates upon interaction with signal molecule

A

histidine

41
Q

True or False: Many operons and regulons are controlled by two component regulatory systems

A

True

42
Q

_____: The exchange of homologous region between two DNA molecules

A

Homologous Recombination

43
Q

In bacteria, gene rearrangements are classified into which two groups?

A
  1. Accidental DNA rearrangements
  2. Programmed DNA rearrangements
44
Q

______ 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

A. Accidental DNA Rearrangements

45
Q

_____ 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

A

B. Programmed DNA Rearrangements

46
Q

_______: the exchange of non-homologous but specific pieces of DNA that mediated by proteins/enzymes (site specific recombinases) that recognize specific sequences

A

Site specific recombination

47
Q

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

A

silent; active

48
Q

True or False: Many silent genes encode variants of the antigens by insertion of new gene into expression locus

A

True

49
Q

True or False: Programmed DNA Rearrangements are a source of consistent antigenic variation

A

True

50
Q

Expression of ___ gene, gene responsible for synthesis of exotoxin in streptolysin, is an example of programmed DNA rearrangment

A

slo

51
Q

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

A

True

52
Q

_____: Switching the expression of some components from on to off

_____: Alters antigenic nature of components

A

Phase Variation
Antigenic Variation

53
Q

True or False: DNA Inversion and Slipped Strand Mispairing are examples of Phase Variation

A

True

54
Q

DNA Recombination and Point mutations are examples of which type of variation?
A. Phase Variation
B. Antigenic Variation

A

B. Antigenic Variation

55
Q

_____ 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

A

D. DNA Inversions

56
Q

E. coli Type 1 Fimbrae are an example of ______
A. DNA Recombination
B. Point Mutations
C. Slipped Strand Mispairing
D. DNA Inversions

A

D. DNA Inversions

57
Q

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?

A

insertion/deletion
- Slipped Strand Mispairing

58
Q

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

A. Slipped-strand mispairings

59
Q

True or False: Opa genes are subject for both phase and antigenic variation

A

True

60
Q

Which type of antigenic variation uses homologous recombination to shuffle antigenic makeup?
A. DNA Recombination
B. Point Mutations

A

A. DNA Recombination

61
Q

Type IV pilus of N. gonnorhoeae and capsule of S. pneumoniae use which type of antigenic variation?

A

DNA recombination

62
Q

____: Simple mutations within the reading frame of genes encoding surface components, can give rise to antigenic variants no longer recognized by host immune system

A

Point mutations

63
Q

Which type of antigenic variation is used by HIV, Influenza A, and M protein in S. pyrogenes?

A

Point mutation

Medical Microbiology (31 decks)

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