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1. Molecular Biology > Control of Gene Expression > Flashcards

Control of Gene Expression Flashcards

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1
Q

where is gene expression regulated?

A

It is regulated at transcription

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2
Q

How does gene expression work?

A

Each different type of cell only uses some of the genes in its total repertoire

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3
Q

What is gene expression?

A

The expression of a different collection of genes in each cell type which causes variation and differentiation in cells

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4
Q

What are gene regulatory proteins?

A

Proteins specialised for switching genes on and off

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5
Q

What does the promoter region of a gene do?

A

It attracts RNA polymerase and correctly orientates the enzyme to begin its task of making an RNA copy of a gene

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6
Q

What do gene regulatory proteins bind to?

A

Regulatory DNA sequences

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7
Q

What acts as a switch to control transcription?

2

A

A combination of regulatory DNA sequence and

Gene regulatory proteins

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8
Q

At what level is the expression of eukaryotic genes controlled?

A

Controlled primarily at the level of initiation of transcription

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9
Q

What controls gene expression in eukaryotes?

A

The combined actions of multiple different transcriptional regulatory proteins

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10
Q

Bacteria regulate the expression of their genes according to what?

A

According to the food sources available in the environment

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11
Q

Why do bacteria adapt so quickly?

A

Operons

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12
Q

What is an operon?

A

A set of adjacent genes in a bacterial genome, transcribed from a single promoter into a single mRNA

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13
Q

What is the function of operons?

A

They group related genes under a common control mechanism which allows bacteria to rapidly adapt to changes in the environment

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14
Q

What are the two examples of operons in E.coli?

A

Trytophan Operon

Lac Operon

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15
Q

Write a note on the trytophan operon

4

A

5 genes which encode for enzyme which manufacture trytophan

These genes are arranged in a cluster on the genome (form an operon)

Genes transcribed from one promoter as 1 long mRNA molecule from which 5 proteins are translated

This operon isn’t needed if bacteria can get trytophan from their environment so it’s shut off

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16
Q

What is the trytophan operator?

2

A

A short DNA sequence within the promoter, upstream of the trytophan operon

Which is recognised by a gene regulatory protein (tryptophan repressor)

17
Q

What is the trytophan repressor?

2

A

A protein that binds to the tryptophan operator, blocking the access of RNA polymerase to the promoter

Shuts off the operon

18
Q

What is required of the tryptophan repressor before it can bind to the operator and stop the operon from being polymerised?
(2)

A

The repressor must bind to the amino acid tryptophan

This binding causes a subtle change in 3D structure which allows it to bind to the operator DNA

19
Q

Define a repressor protein.

A

A protein that switches genes off or represses them

20
Q

Define an activator protein

A

A protein that switches genes on or activates them

21
Q

Write a note on the lac operon

3

A

Operon that encodes proteins required to import and digest lactose

Consists of 3 genes: lacZ, lacY and lacA

All genes under control of 1 promoter

22
Q

Does the lac operon require induction to be expressed

A

No it doesn’t

23
Q

What are the four lac genes?

A

lac Y

lac Z

lac A

lac l

24
Q

What does the lac Y gene code for?

A

Codes for lactose permease

25
Q

What does lactose permease do?

A

It transports lactose into the cell

26
Q

What does the lac Z and lac A genes code for?

A

They code for the enzymes b-galactosidase and transacetylase

27
Q

What does b-galactosidase and transacetylase do?

A

They split lactose into galactose and glucose

28
Q

What does the lac l gene do?

2

A

It’s located outside the operon

It codes for a repressor protein which can switch off the lac operon by binding to the operator sequence

29
Q

Where is the lac operon operator sequence found?

2

A

Lies within the promoter for lactose operon

Just upstream of the operon genes

30
Q

What is lactose split into?

2

A

Glucose

Galactose

31
Q

What is an intermediate between lactose and glucose and galactose?

A

Allolactose

32
Q

What is allolactose?

A

An isomer of lactose

33
Q

What does allolactose do?

2

A

It binds to the lac operon repressor protein - causing a change in conformation

This prevents the repressor protein from working and binding to the operator sequence

1. Molecular Biology (12 decks)

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