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Mbg 2040 > Control of Gene Expression in Bacteria > Flashcards

Control of Gene Expression in Bacteria Flashcards

1
Q

What are constitutively expressed genes

A

genes that specify gene products essential for living cells, that are continuously expressed in most cells

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2
Q

What are inducible and repressible genes

A

some gene products are only needed under certain conditions, so regulatory mechanisms allow synthesis of these gene products only when needed (inducible) or shut down genes when no longer needed (repressible)

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3
Q

What level of regulation is the concern in this course

A

regulation at the level of transcription initiation

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4
Q

What is required of regulation in the initiation transcription level

A

binding of proteins (transcription factors) to the DNA

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5
Q

What are DNA binding proteins in relation to gene regulation in transcription initiation

A

can be activators or repressors
- contain domains that recognize DNA sequences in combination with grooves in DNA
- non covalent bonding
- bind to the promoter of a gene
- recruits RNA polymerase

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6
Q

Transcription in bacteria is regulated by _____________

A

operons

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7
Q

Regulation of transcription is controlled by ___________ _______________

A

regulator proteins
*and the promoter/operator complex

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8
Q

Where do regulator proteins bind

A

the promoter (or operon)

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9
Q

What is the function of negative regulatory proteins

A

inhibit transcription

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10
Q

What is the function of positive regulator proteins

A

active transcription

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11
Q

What are inducible operons

A

transcription of the operon is normally off, and something happens to turn it on

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12
Q

What are repressible operons

A

transcription of the operon is normally on, and something happens to turn it off

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13
Q

How does a regulator protein function to keep transcription turned off (negative inducible operon)

A

blocks the binding of RNA polymerase

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14
Q

How can transcription involving a negative inducible operon be restored if being repressed

A

a small molecule called an inducer binds to the inhibitor/repressor and inactivates it, so the repressor can no longer bind to DNA and RNA poly can activate transcription

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15
Q

How does a regulator protein function to turn off transcription (negative repressible operon)

A

can’t bind to the promoter/operator complex without a cofactor (repressor is inactive in the absence of a cofactor)
- small molecule called a corepressor binds to the repressor and allows the repressor/corepressor complex to bind to the operator to inhibit transcription

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16
Q

How does a regulator protein function to positively control transcription

A

regulatory protein is an activator (think positive) and binds to operator to induce txn
- binds upstream of promotor an enhances the binding of RNA poly to the promoter

17
Q

What is an example of a positive activator of transcription

A

catabolite activator protein (CAP) is a positive activator of transcription

18
Q

In relation to the Lac operon, how does negative inducible control occur

A

regulator is an inhibitor
allolactose inactivates inhibitor

19
Q

In relation to the Lac operon, how does positive control occur

A

CAP+cAMP enhances transcription

20
Q

What is coordinate induction

A

the simultaneous synthesis of several proteins by a specific molecule called the inducer

21
Q

What are the three enzymes in the operon involving metabolism of lactose via E. coli

A

Permase (lacY)
B-galatosidase (lacZ)
thiogalactoside transacetylase (lacA)

22
Q

Read the slides about the Lac operon and understand them*****

A

see slides 18-20 in “control of gene expression in bacteria” slideshow

23
Q

What is cis regulation

A

control gene expression only on the same piece of DNA

24
Q

What is trans regulation

A

control gene expression of other DNA molecules

25
Q

The promoter sequence for the operon is ___________ acting on lacZ

A

cis

26
Q

The repressor protein is ____________ acting on lacZ

A

trans

27
Q

Non functional mutations are noted with what symbol

A

”-“

28
Q

Functional mutations are noted with what symbol

A

”+”

29
Q

Why is glucose the preferred source of energy in bacteria

A

it is easier to metabolize

30
Q

When glucose is present, bacteria will turn off other pathways; this is called…

A

catabolite repression

31
Q

Positive glucose metabolism in bacteria resulting in repression of other pathways; this is called…

A

positive control

32
Q

Levels of __________ are inversely proportional to glucose levels

A

cAMP

33
Q

If glucose is low, cAMP is

A

high
and vice versa

34
Q

Since levels of cAMP impact expression of lac operon, when glucose is high and cAMP is low, what happens to lac operon expression

A

significantly reduced
(due to reduced affinity of poly to promoter)

Mbg 2040 (13 decks)

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