Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

microbiology > molecular microbiology > Flashcards

molecular microbiology 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
unit of transcription ?
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
26
3 types of rRNA ?
16S, 23S, and 5S.
27
is rRNA and tRNA stable ?
yes
28
what is tRNA co transcribed with ?
rRNA or other tRNA's
29
do mRNA have a short or long half life and what is it ?
short and a few minutes , to prevent the production of uneeded proteins
30
prokarytoes often have genes clustered together , when transcribed are these done together or not ?
transcribed all at once as a single mRNA. This produces a polycistronic mRNA
31
operon ?
group of related genes co-transcribed on a polycistronic mRNA which allows for expression of multiple genes to be coordinated.
32
how many different domains does RNA polymerase have ?
3
33
what are the mechanisms for controlling protein activity ?
enzymes include feedback inhibition , degradation , protein to protein interactions and covalent modifications. These controls are set up during gene expression and translation.
34
what does the regulation of transcription usually require ?
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
how is the specificity achieved of protein binding to DNA ?
provided by interactions between amino acid side chains and chemical groups on the bases and sugar–phosphate backbone of DNA
36
major groove of DNA ?
main site of protein binding. The inverted repeats frequently are binding site for regulatory proteins
37
homodimeric proteins ?
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
what are the 3 outcomes after DNA bonding ?
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
negative control uses an inducer and a repressor what are these ?
An Inducer is a substance that induces enzyme synthesis. A Core-repressor is a substance that represses enzyme synthesis`
40
effectors ?
collective term for inducers and repressors. Effectors affect transcription indirectly by binding to specific DNA-binding proteins.
41
where do repressor bind to ?
allosteric repressor protein | – Allosteric repressor becomes active and binds to region of DNA near promoter called the operator
42
where is an operon located >
located downstream of the promoter. Transcription is physically blocked when repressor binds to operator.
43
what does the addition of an inducer do ?
inactivates repressor, and transcription can proceed
44
the enzymes affected by repression make up what if the total proteins ?
a small fraction
45
what does repression normally affect in terms of enzymes ?
anabolic like arginine biosynthesis
46
induction ?
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
positive control ?
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
what is the strength of the binding to RNA polymerase of promoters ?
weakly
49
what does the activator protein do ?
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
how are the genes for maltose spread out ?
over the chromosome in several operons
51
what does each operon have ?
an activator bindings site
52
regulon
Multiple operons are controlled by the same regulatory protein
53
are regulon just for positive control systems ?
nope , negative as well
54
global control systems ?
regulate expression of many different genes simultaneously.
55
catabolite repression ?
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
diauxic growth ?
two exponential growth phases. occurs in growth of E.coli on a mixture of glucose and lactose
57
cyclic AMP and CRP ?
– 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
how do prokaryotes regulate cellular metabolism ?
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
what are the 2 different proteins that make this up ?
– 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
examples of 2 component systems ?
phosphate assimilation, nitrogen metabolism, and osmotic pressure response. Archea as well have this
61
chemotaxins ?
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
respnnse to signal ?
– Sensory proteins in cytoplasmic membrane sense attractants and repellents – Methyl-accepting chemotaxis proteins (MCPs) • Bind attractant or repellent and initiate flagellar rotation
63
controlling flagellar rotation
– Controlled by CheY protein • CheY results in counterclockwise rotation and runs • CheY-P results in clockwise rotation and tumbling
64
adaptation ?
– Feedback loop • Allows the system to reset itself to continue to sense the presence of a signal • Involves modification of MCPs
65
phototaxis ?
: movement toward light | • Light sensor replaces MCPs
66
aerotaxis ?
movement toward oxygen | • Redox protein monitors oxygen level
67
quorum sensing ?
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
specific autoinducer molecule ?
– 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
– Acyl homoserine lactone (AHL
first autoinducer identified
70
when was quorum sensing firsy identified ?
mechanism regulating light production in bacteria including Aliivibrio fischeri . Lux operon encodes bioluminescence
71
examples of quorum sensing?
– Virulence factors | – Switching from free-living to growing as a biofilm
72
is quroum sensing available in all domains ?
present in some microbial eukaryotes , Quorum sensing likely exists in Archaea. Yes
73
example of virulence factors ?
– 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
what is biofilm production an example of ?
social behaviour in bacteria
75
list some global control networks ?
``` – 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.
© 2025 Bold Learning Solutions. Terms and Conditions