Lecture 15 and 16 Flashcards

(41 cards)

1
Q

Information is the result of…

A

Processing, manipulating and organising data

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2
Q

How to change prokaryotic gene expression?

A

Change the RNA polymerase sigma factor

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3
Q

What does changing the RNA polymerases sigma factor do?

A

Directs polymerase to different promoters

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4
Q

What does normal sigma factor do?

A

sigma-70 binds to RNA polymerase and recognizes sequence in promoter to initate transcription

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5
Q

What happens when sigma factor 70 is heated?

A

heat shock disables it

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6
Q

What happens when heat shock disables sigma factor 70?

A

rpoH gene product, sigma 32, binds to sequence in promoter of heat shock gene and starts transcription

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7
Q

What is negative control of prokaryotic gene expression?

A

Repressor protein(s) bind to DNA and inhibit transcription

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8
Q

What is positive control of prokaryotic gene expression?

A

Activator protein(s) bind to DNA and enhance transcription

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9
Q

What genes have a level of encoded protein that vaires?

A

Regulated genes

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10
Q

What genes are switched off until required?

A

Inducible genes

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11
Q

What genes are switched on until not required?

A

Repressible genes

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12
Q

What genes encode a constant amount of protein?

A

Constitutive genes

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13
Q

How were lactose utilization genes identified?

A

Complementation analysis of mutants

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14
Q

Who isolated Lac- mutants unable to utilize lactose?

A

Jacob, Monod et al.

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15
Q

What three genes were identified as lactose utilization genes?

A

LacZ, lacY, lacA

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16
Q

What experimental evidence was there for a repressor protein for the lac genes?

A

Isolated mutant in lacI gene which synthesised lac permease in absence of lactose–> lacI is repressor

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17
Q

How is enzyme synthesis of lac genes triggered?

A

Inducer causes B-galactosidase synthesis

18
Q

How does the inducer work

A

It binds to repressor so repressor cannot bind DNA

19
Q

What type of effect is the inducer having on the repressor?

A

Allosteric effect

20
Q

What is an operon?

A

two or more genes co-ordinately regulated by a single promoter and terminator

21
Q

What is an operator?

A

A section of DNA that binds to regulator protein in an operon

22
Q

List the sites in order.

A

Regulator gene (lacI)
Promoter
Operator
LacZ

23
Q

What does lacZ code for?

A

B-galactosidase

24
Q

What does lacY code for?

25
What does lacA code for?
Transacetylase
26
How does lacI work as a regulator gene?
It codes for repressor protein which binds to operator, lactose binds and inactivates it
27
When glucose is scarce and lactose is present, what levels are high?
cAMP
28
cAMP binds to what to make what?
Inactive CAP | Active CAP
29
What type of control increases lac gene transcription using CRP bound to regulatory region?
Positive control
30
What happens if there are changes in the operator?
Repressor cannot bind, lac enzymes synthesised constitutively
31
What is a trans effect?
Genes are regulated even when two DNA segments are not physically adjacent
32
What is a cis-acting element?
A DNA segment that must be adjacent to the genes it regulates
33
What do trans acting elements do?
Diffuse through cytoplasm, act as target DNA sites on any DNA moleule
34
What can cis acting elements do?
Only influence expression of adjacent genes on the same DNA molecule
35
Do eukaryotes have operons?
no
36
What affects expression in eukaryotes?
Chromatin
37
What are 4 regulatory protein types in eukaryotes?
Activators Coactivators Basal transcription factors Repressors
38
What do activators do?
Bind to genes at enhancer sites, determine which genes are switched on and increase speed
39
What are coactivators?
Adaptor molecule that integrate signals from activators
40
What do basal transcription factors do?
Position RNA polymerase at the start of the protein-coding region of a gene
41
What do repressors bind to in eukaryotes?
Silencer sites on genes