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Chromosomes and genes > Lecture 15 and 16 > Flashcards

Lecture 15 and 16 Flashcards

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?

A

Permease

25
Q

What does lacA code for?

A

Transacetylase

26
Q

How does lacI work as a regulator gene?

A

It codes for repressor protein which binds to operator, lactose binds and inactivates it

27
Q

When glucose is scarce and lactose is present, what levels are high?

A

cAMP

28
Q

cAMP binds to what to make what?

A

Inactive CAP

Active CAP

29
Q

What type of control increases lac gene transcription using CRP bound to regulatory region?

A

Positive control

30
Q

What happens if there are changes in the operator?

A

Repressor cannot bind, lac enzymes synthesised constitutively

31
Q

What is a trans effect?

A

Genes are regulated even when two DNA segments are not physically adjacent

32
Q

What is a cis-acting element?

A

A DNA segment that must be adjacent to the genes it regulates

33
Q

What do trans acting elements do?

A

Diffuse through cytoplasm, act as target DNA sites on any DNA moleule

34
Q

What can cis acting elements do?

A

Only influence expression of adjacent genes on the same DNA molecule

35
Q

Do eukaryotes have operons?

A

no

36
Q

What affects expression in eukaryotes?

A

Chromatin

37
Q

What are 4 regulatory protein types in eukaryotes?

A

Activators
Coactivators
Basal transcription factors
Repressors

38
Q

What do activators do?

A

Bind to genes at enhancer sites, determine which genes are switched on and increase speed

39
Q

What are coactivators?

A

Adaptor molecule that integrate signals from activators

40
Q

What do basal transcription factors do?

A

Position RNA polymerase at the start of the protein-coding region of a gene

41
Q

What do repressors bind to in eukaryotes?

A

Silencer sites on genes

Chromosomes and genes (10 decks)

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