bsc2010 ch 18 & 19 prokaryotic gene regulation

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gene regulation

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this is important since we have around 22,000 genes or 3 billion base pairs

  • alter gene expression in response to changing environment (adaptation)

  • conserving resources

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transcriptional regulation

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this is the primary point of control especially among bacteria

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19 Terms

1

gene regulation

this is important since we have around 22,000 genes or 3 billion base pairs

  • alter gene expression in response to changing environment (adaptation)

  • conserving resources

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2

transcriptional regulation

this is the primary point of control especially among bacteria

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3

transcriptional control

type of gene expression in bacteria

control of mRNA transcription, saves energy by being slow but efficient, most common point of control

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4

translational control

type of gene expression in bacteria

cells can quickly change which proteins are produced, mRNA is already present

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5

post-translational control

type of gene expression in bacteria

rapid response; energetically expensive

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6

negative control

when a regulatory protein such as a repressor binds to DNA and shuts down transcription

  • trp and lac operons

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7

positive control

when a regulatory protein such as an activator protein binds to DNA and triggers transcription

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8

operator

in the DNA, this is a segment of it that acts like a switch to turn a gene on or off

<p>in the DNA, this is a segment of it that acts like a switch to turn a gene on or off</p>
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9

promoter

in the DNA, this is a segment of it that RNA polymerase binds to and initiates transcription, before the operator

<p>in the DNA, this is a segment of it that RNA polymerase binds to and initiates transcription, before the operator</p>
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10

operon

entire stretch of DNA including the operator, the promoter, and the genes that they control

<p>entire stretch of DNA including the operator, the promoter, and the genes that they control</p>
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11

repressor

protein able to switch an operon off and prevents gene transcription by binding to the operator DNA and blocking RNA polymerase

  • form of negative control

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12

inducible operon

usually off, an inductor deactivates the repressor and turns on transcription

  • lac operon

  • catabolic

  • active form of repressor protein

  • negative gene control (prevents expression)

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13

repressible operon

usually on, binding of a repressor to the operator to stop transcription

  • trp operon

  • anabolic

  • inactive form of repressor protein

  • negative gene control (prevents expression)

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14

lac operon

inducible operon who’s main objective is to break down lactose

  • lac operon turned on by inducer inactivating

when lactose is absent: the active repressor binds to the operator and blocks the RNA polymerase’s path

when lactose is present: the lactose (inducer) binds to the repressor and becomes an inactive repressor, changing the protein’s shape and making it denatured; the operator isn’t blocked so RNA polymerase can continue to make the enzyme able to break lactose down

<p>inducible operon who’s main objective is to break down lactose </p><ul><li><p>lac operon turned on by inducer inactivating</p></li></ul><p><strong>when lactose is absent: </strong>the active repressor binds to the operator and blocks the RNA polymerase’s path</p><p><strong>when lactose is present: </strong>the lactose (inducer) binds to the repressor and becomes an inactive repressor, changing the protein’s shape and making it denatured; the operator isn’t blocked so RNA polymerase can continue to make the enzyme able to break lactose down</p>
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15

corepressor

molecule that cooperates with the repressor protein to switch the operon off

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16

trp operon

repressible operon who’s main job is to make/synthesize tryptophan

  • when tryptophan is absent: by nature, the inactive repressor is already denatured so the RNA polymerase can proceed

  • when tryptophan is present: the tryptophan acts as a corepressor, binding to the repressor and making it an active repressor, blocking the RNA polymerase

  • this tells them that there’s enough tryptophan made and making more would waste resources

<p>repressible operon who’s main job is to make/synthesize tryptophan</p><ul><li><p><strong>when tryptophan is absent: </strong>by nature, the inactive repressor is already denatured so the RNA polymerase can proceed</p></li><li><p><strong>when tryptophan is present: </strong>the tryptophan acts as a corepressor, binding to the repressor and making it an active repressor, blocking the RNA polymerase</p></li><li><p>this tells them that there’s enough tryptophan made and making more would waste resources</p></li></ul>
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17

activator

stimulatory protein that aids positive gene control

  • binds to the DNA sequence, interacts with RNA polymerase to make transcription happen quicker

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18

AraC

an activator protein that transcribes the ara operon when arabinose is present

  • also acts as a repressor to prevent transcription when arabinose is not present

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19

arabinose

positive regulator for the ara operon, where the AraC protein binds to _____________

  • with ________ and AraC together, transcription is sped up

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