Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

microbiology > molecular microbiology > Flashcards

molecular microbiology Flashcards

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards
1
Q

what did Francois Jacob and Jacques Monod win ?

A

2 Croix De Guerre and 2 Nobel Prizes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what did they do ?

A

Together they originated the idea that the control of enzyme levels in all cells occurs through regulation of transcription.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

replication of DNA ?

A

nucleus and uses DNA polymerase to form an exact copy of DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

transcription ?

A

occurs in the nucleus and a single strand of RNA is composed using RNA polymerase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

translation ?

A

the ribosomes the messenger RNA is a template for protein synthesis.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

in a picture what does a large white blob indicate ?

A

original location and size of E.coli prior to it’s lysis.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

supercoiled DNA ?

A

DNA is further twisted to save space

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

negative supercoiling ?

A

double helix is under wound

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

positive supercoiling ?

A

double helix is overwound

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

relaxed DNA ?

A

DNA has number of turns predicted by number of base pairs. Negative supercoiling is predominantly found in nature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

DNA gyrase ?

A

introduces supercoils into DNA and acts as a catalyst

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

how does supercoiling of DNA occur ?

A

one part of the circle is laid over the other , the helix makes contact in 2 places. The unbroken helix is passed through the break. Following DNA gyrase activity , 2 negative supercoils result.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

is this process random ?

A

not random as it allows access to the most used genes in the genome.Gene regulation is important as it is conserving scarce nutrients

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

chromosomes ?

A

large and they encode for all essential genes and more. Chromosome is a genetic element with “housekeeping” genes. The presence of essential genes is necessary for a genetic element to be called a chromosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what are transposable elements ?

A

Segment of DNA that can move from one site to another site on the same or a different DNA molecule. They are inserted into other DNA molecules
Three main types:

Insertion sequences
Transposons
Special viruses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

plasmids ?

A

small, there’s many copies and they are nonessential but advantageous beneficial genes (e.g. antibiotic resistance). Plasmids replicate separately from chromosomes and most are circular. They are not extracellular unlike viruses. Plasmid is a genetic element that is expendable and rarely contains genes for growth under all conditions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

do viruses contain RNA or DNA and shape ?

A

can be either , can be linear or circular , double or single stranded.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

give an example of an advantageous gene in plasmids ?

A

antibiotic resistance in streptomyces.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what are sigma factors ?

A

recognize two highly conserved regions of promoter. The two regions within promoters that are highly conserved are:
– Pribnow box: located 10 bases before the start of transcription (–10 region)
– –35 region: located ~35 bases upstream of transcription

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what foes RNA polymerase have an interaction with ?

A

bacterial promoter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

is there just one sigma factor present ?

A

There are multiple sigma factors for different scenarios. The numbers vary between organisms. E. coli has 7, P. aeuginosa has 18, Streptomyces spp. have hundreds.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what does the sigma recognise ?

A

the promotor and initiation site

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

describe transcription with sigma ?

A

The sigma recognises the promotor and initiation site. Transcription can therefore begin and the sigma is released. The RNA chain grows. The termination site causes the chain to stop growing in length and the polymerase and RNA are released

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

the prokaryotic transcripts are polycistronic , what does this mean ?

A

this means the messenger RNA can encode more than one polypeptide separately within the same RNA molecule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

unit of transcription ?

A

the unit of chromosome bounded by sites where transcription of DNA to RNA is initiated and terminated. Most genes encode for proteins, but some RNAs are not translated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

3 types of rRNA ?

A

16S, 23S, and 5S.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

is rRNA and tRNA stable ?

A

yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what is tRNA co transcribed with ?

A

rRNA or other tRNA’s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

do mRNA have a short or long half life and what is it ?

A

short and a few minutes , to prevent the production of uneeded proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

prokarytoes often have genes clustered together , when transcribed are these done together or not ?

A

transcribed all at once as a single mRNA. This produces a polycistronic mRNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

operon ?

A

group of related genes co-transcribed on a polycistronic mRNA which allows for expression of multiple genes to be coordinated.

32
Q

how many different domains does RNA polymerase have ?

A

3

33
Q

what are the mechanisms for controlling protein activity ?

A

enzymes include feedback inhibition , degradation , protein to protein interactions and covalent modifications. These controls are set up during gene expression and translation.

34
Q

what does the regulation of transcription usually require ?

A

proteins that can bind to DNA. These will be small molecules that influence the binding of regulatory proteins to DNA. Proteins actually regulate transcription.

35
Q

how is the specificity achieved of protein binding to DNA ?

A

provided by interactions between amino acid side chains and chemical groups on the bases and sugar–phosphate backbone of DNA

36
Q

major groove of DNA ?

A

main site of protein binding. The inverted repeats frequently are binding site for regulatory proteins

37
Q

homodimeric proteins ?

A

proteins that are composed of 2 identical polypeptides. The protein dimers interact with the inverted repeats of DNA and each of the polypeptides binds to one inverted repeat.

38
Q

what are the 3 outcomes after DNA bonding ?

A
  1. DNA-binding protein may catalyze a specific reaction on the DNA molecule (i.e., transcription by RNA polymerase)
  2. The binding event can block transcription
    (negative regulation)
  3. The binding event can activate transcription
    (positive regulation)
39
Q

negative control uses an inducer and a repressor what are these ?

A

An Inducer is a substance that induces enzyme synthesis. A Core-repressor is a substance that represses enzyme synthesis`

40
Q

effectors ?

A

collective term for inducers and repressors. Effectors affect transcription indirectly by binding to specific DNA-binding proteins.

41
Q

where do repressor bind to ?

A

allosteric repressor protein

– Allosteric repressor becomes active and binds to region of DNA near promoter called the operator

42
Q

where is an operon located >

A

located downstream of the promoter. Transcription is physically blocked when repressor binds to operator.

43
Q

what does the addition of an inducer do ?

A

inactivates repressor, and transcription can proceed

44
Q

the enzymes affected by repression make up what if the total proteins ?

A

a small fraction

45
Q

what does repression normally affect in terms of enzymes ?

A

anabolic like arginine biosynthesis

46
Q

induction ?

A

production of an enzyme in response to a signal. It typically affects catabolic enzymes (e.g., lac operon). The enzymes are synthesized only when they are needed and this means no wasted energy.

47
Q

positive control ?

A

when a regulator protein activates the binding of RNA polymerase to DNA. This occurs in maltose catabolism in E. coli. The maltose activator protein cannot bind to DNA unless it first binds maltose. The activator proteins bind specifically to certain DNA sequence. This is called activator-binding site not operator

48
Q

what is the strength of the binding to RNA polymerase of promoters ?

A

weakly

49
Q

what does the activator protein do ?

A

helps RNA polymerase recognise the promoter. This may cause a change in the DNA structure as it may interact directly with RNA polymerase. The activator-binding site may be close to the promoter or be several hundred base pairs away.

50
Q

how are the genes for maltose spread out ?

A

over the chromosome in several operons

51
Q

what does each operon have ?

A

an activator bindings site

52
Q

regulon

A

Multiple operons are controlled by the same regulatory protein

53
Q

are regulon just for positive control systems ?

A

nope , negative as well

54
Q

global control systems ?

A

regulate expression of many different genes simultaneously.

55
Q

catabolite repression ?

A

is an example of global control. The synthesis of unrelated catabolic enzymes is repressed if glucose is present in growth medium. lac operon is under control of catabolite repression. This ensures that the “best” carbon and energy source is used first

56
Q

diauxic growth ?

A

two exponential growth phases. occurs in growth of E.coli on a mixture of glucose and lactose

57
Q

cyclic AMP and CRP ?

A

– In catabolite repression, transcription is controlled by an activator protein and is a form of positive control.
– Cyclic AMP receptor protein (CRP) is the activator protein
– Cyclic AMP is a key molecule in many metabolic control systems
• Derived from a nucleic acid precursor
• Is a regulatory nucleotide
Dozens of catabolic operons are affected by catabolite repression
– Enzymes for degrading lactose, maltose, and other common carbon sources
Flagellar genes are also controlled by catabolite repression
– No need to swim in search of nutrients

58
Q

how do prokaryotes regulate cellular metabolism ?

A

in response to environmental fluctuations. The external signal is transmitted directly to the target . The external signal is then detected by sensor and transmitted to regulatory machinery (signal transduction).Most signal transduction systems are two-component regulatory systems

59
Q

what are the 2 different proteins that make this up ?

A

– Sensor kinase (in cytoplasmic membrane): detects environmental signal and autophosphorylates
– Response regulator (in cytoplasm): DNA-binding protein that regulates transcription

They also has feedback loop and this terminates the signal

60
Q

examples of 2 component systems ?

A

phosphate assimilation, nitrogen metabolism, and osmotic pressure response. Archea as well have this

61
Q

chemotaxins ?

A

This is a modified two-component system used in chemotaxis to
– Sense temporal changes in attractants or repellents
– Regulate flagellar rotation
• Three main steps
– Response to signal
– Controlling flagellar rotation
– Adaptation

62
Q

respnnse to signal ?

A

– Sensory proteins in cytoplasmic membrane sense attractants and repellents
– Methyl-accepting chemotaxis proteins (MCPs)
• Bind attractant or repellent and initiate flagellar rotation

63
Q

controlling flagellar rotation

A

– Controlled by CheY protein
• CheY results in counterclockwise rotation and runs
• CheY-P results in clockwise rotation and tumbling

64
Q

adaptation ?

A

– Feedback loop
• Allows the system to reset itself to continue to sense the presence of a signal
• Involves modification of MCPs

65
Q

phototaxis ?

A

: movement toward light

• Light sensor replaces MCPs

66
Q

aerotaxis ?

A

movement toward oxygen

• Redox protein monitors oxygen level

67
Q

quorum sensing ?

A

Prokaryotes can respond to the presence of other cells of the same species. Quorum sensing is a mechanism by which bacteria assess their population density. It ensures that a sufficient number of cells are present before initiating a response that, to be effective, requires a certain cell density

68
Q

specific autoinducer molecule ?

A

– Diffuses freely across the cell envelope
– Reaches high concentrations inside cell only if many cells are near
– Binds to specific activator protein and triggers transcription of specific genes

69
Q

– Acyl homoserine lactone (AHL

A

first autoinducer identified

70
Q

when was quorum sensing firsy identified ?

A

mechanism regulating light production in bacteria including Aliivibrio fischeri . Lux operon encodes bioluminescence

71
Q

examples of quorum sensing?

A

– Virulence factors

– Switching from free-living to growing as a biofilm

72
Q

is quroum sensing available in all domains ?

A

present in some microbial eukaryotes , Quorum sensing likely exists in Archaea. Yes

73
Q

example of virulence factors ?

A

– Escherichia coli O57:H7
• Shiga toxin–producing strain
• Produces AHL AI-3
• Epinephrine plus norepinephrine plus AI-3 bind to sensor molecules in plasma membrane. This activates motility, enterotoxin production, and production of virulence proteins

74
Q

what is biofilm production an example of ?

A

social behaviour in bacteria

75
Q

list some global control networks ?

A 
–	Aerobic and anaerobic respiration
–	Catabolite repression
–	Nitrogen utilization
–	Oxidative stress
–	SOS response 
–	Heat shock response

microbiology (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions