6.5 Gene Regulation in prokaryotes Flashcards

1
Q

Prokaryotes must be able to _____ which genes are expressed at any given time

A

Regukate

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2
Q

How can genes be turned on or off?

A

Based on environmental and internal cues

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3
Q

What does turning a gene “on” or “off” mean? What does this allow for?

A

Whether or not transcription will take place

- cell specialization

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4
Q

What are operons?

A
  • a group of genes that can be turned on or off
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5
Q

What are the three parts of operons?

A
  • Promoter
  • operator
  • genes
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6
Q

What is the promoter of an operon?

A
  • where RNA polymerase can attach
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7
Q

What is the operator of an operon?

A

The on/off switch

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8
Q

What do genes do in an operon?

A

Codes for related enzymes in pathways

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9
Q

Operons can be _____ or ______

A

Repressive or inducible

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10
Q

What does repressible operons mean? (2)

A
  • on to off

- transcription is usually in, but can be repressed, or stopped

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11
Q

What does an inducible operon mean? (2)

A
  • off to on

- transcription is usually off, but can be induced, or started

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12
Q

What is a regulatory gene? (2)

A
  • produces a repressor protein that binds to the operator to block RNA polymerase from transcribing the gene
  • always exposed, but at low levels
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13
Q

Is binding of a repressor to an operator reversible?

A

Yes

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14
Q

The trp operon is a _____ (repressible/inducible) operon.

A

Repressible

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15
Q

What does the trp operon control?

A
  • controls the synthesis of tryptophan in bacteria
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16
Q

What occurs in the trp operon? (3)

A
  1. Since it is repressible, transcription is active
  2. It can be switched off by the trp repressor
    - an Allosteric enzyme that is only active when tryptophan binds to it
17
Q

What occurs if there is too much tryptophan build up in bacteria?

A
  1. Tryptophan is more likely to bind to the repressor, turning in active
  2. This will temporarily shit off transcription for tryptophan
18
Q

The lac operon is an ______ operon

A

Inducible

19
Q

What does the lac operon control the synthesis of?

A

Lactase, an enzyme that digests lactose (milk sugar)

20
Q

Since the lac operon is inducible, transcription is ___

A

Off

21
Q

What is the lac repressor bound to? Which side?

A

The operator, Allosterically

22
Q

What is the inducer for the lac repressor?

A

Allolactose

23
Q

What occurs to the lac repressor when allolactose is present?

A
  1. Allolactose will bind to the lac repressor and turn the lac repressor off (allosterically active)
24
Q

After the allolactose binds to the lac repressor and turns it off, what can now occur?

A

The gene can now be transcribed