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Biology > Gene Regulation in bacteria > Flashcards

Gene Regulation in bacteria Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Gene regulation

A

The phenomenon in which the level of gene expression can vary under different conditions

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2
Q

Constitutive genes

A

Unregulated genes that have constant level of expression (ex. polymerase “house keeping genes”)

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3
Q

What are a few common process that are regulated at the genetic level?

A
  1. Metabolism
  2. Response to environmental stress
  3. Cell division
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4
Q

_________ in bacteria can occur at any step in gene expression

A

Gene regulation

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5
Q

In bacteria the common way to regulate gene expression is by influencing the rate at which __________ is initiated

A

Transcription

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6
Q

Since gene expression is usually referred to being _______ or _______ at the level of transcription this means that the rate of RNA synthesis can be increased or decreased

A

Increased or Decreased

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7
Q

What are the two regulatory proteins that are involved in transcriptional regulation?

A
  1. A repressor
  2. An activator
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8
Q

Repressor (negative regulator)

A

A regulatory protein that binds to the DNA & stops (inhibits) transcription

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9
Q

An activator (positive regulatory)

A

A regulatory protein that increased the rate of transcription

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10
Q

Transcriptional regulation by a repressor is called what?

A

Negative control

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11
Q

Transcriptional regulation by an activator is called what?

A

Positive control

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12
Q

________ molecules play a crucial role in transcriptional regulation where they bind to an activator or repressor which causes the activator or repressor to bind to the DNA

A

Small effector molecules

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13
Q

What are the types of effector molecules?

A
  1. An inducer
  2. A corepressor
  3. An inhibitor
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14
Q

An inducer

A

Is a small effector molecule that causes transcription to increase

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15
Q

How does an inducer cause transcription to increase?

A

They can bind to a repressor protein & prevent it from binding to the DNA or it can bind to an activator protein & cause it to bind to the DNA

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16
Q

Inducible genes

A

Genes that are regulated by inducers

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17
Q

A corepressor

A

A small effector molecule that binds to a repressor which causes the repressor to bind to the DNA & decrease transcription (activates the repressor)

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18
Q

An inhibitor

A

Binds to an activator protein & prevents it from binding to the DNA (inhibit the activator)

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19
Q

A corepressor & inhibitor __________ transcription

A

Decrease

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20
Q

Repressible genes

A

Genes that are regulated by corepressor or inhibitors

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21
Q

Enzyme adaptation

A

When a particular enzyme is produced in a cell only after a cell has been exposed to the substrate for that enzyme (when a bacterium isn’t exposed to a particular substance it doesn’t make enzymes needed to metabolize that substance)

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22
Q

_______ & _______ study enzyme adaptation by observing lactose metabolism in E. Coli (studying the lac operon)

A

Jacob & Monod

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23
Q

The _______ encodes proteins that are involved in lactose metabolism

A

Lac operon

24
Q

An operon

A

Contains two or more genes that are transcribed from a single promoter

25
Q

An operon encodes a ____________ mRNA

A

Polycistronic mRNA

26
Q

Polycistronic mRNA

A

An mRNA that contains the sequences of two or more genes

27
Q

What is an advantage of an operon ?

A

It coordinated regulation of group genes

28
Q

Lac Operon

A

Contains a CAP site, promoter (lacP), operator site (lacO), & there protein -encoding genes which are: lacZ, lacY, & lac A, also has a terminator region

29
Q

The lacZ encodes what ?

A

An enzyme called B-galactosidase which is an enzyme that cuts lactose into galactose & glucose

30
Q

B-galactosidase also does what as a side reaction?

A

Converts lactose into allolactose (which is an inducer of the lac operon)

31
Q

The lacY gene encodes what?

A

Lactose permease- which is a membrane protein required for the active transport of lactose into the cytoplasm of the bacterium (transport lactose)

32
Q

The ______ & _______ site are short DNA segments that function in gene regulation

A

The CAP site & Operator Site

33
Q

The CAP site

A

Is a DNA sequence that is recognized by an activator

34
Q

The operator site (operator)

A

Is a sequence of bases that provide a binding site for a repressor (bound by lacl & goes through negative regulation)

35
Q

_______ is bound by RNA polymerase

A

Promoter

36
Q

_______ is a repressor that inhibits RNA polymerase (Its not located in the operon but outside it (right before it))

A

lacl

37
Q

The ______ isn’t part of the lac operon & it has it’s own promoter, the i promoter

A

lacl

38
Q

The ______ encodes the lac repressor

A

lacl

39
Q

The ________ can be regulated by the lac repressor under negative control

A

Lac Operon

40
Q

When __________ is absent then the lac repressors binds to the operator site & prevents RNA polymerase from transcribing the lacZ, lacY, & lacA, genes

A

Allolactose

41
Q

When _______ is available it can bind to the lac repressor & prevent it from binding to the operator site & allow RNA polymerase to bind & transcribe lacZ, lacY, & lacA genes

A

Allolactose (is an inducer)

42
Q

Even though when the ________ binds to the operator site & inhibits transcription it doesn’t completely inhibit transcription instead there is basal transcription occurring when low levels of B-galalctosidase, lactose permease, & transacetylase

A

lac repressor

43
Q

The __________ doesn’t completely inhibit the lac operon because it still detect if lactose is present so that when lactose is present B-galactosidase can convert it into allolactose & remove the repressor

A

lac repressor

44
Q

Describe the first 2 steps in the cycle of lac operon induction & repression

A
  1. When lactose becomes available a small amount is take up & converted to allolactose by B-galalactosidase. The allolactose binds to the repressor causing the repressor to fall off the operator site
  2. lac operon proteins are synthesis. this promotes the efficient uptake & metabolism of lactose
45
Q

Describe the last 2 steps in the cycle of lac operon induction & repression

A
  1. The lactose is depleted. Allolactose levels in decrease and allolactose is released from the repressor, allowing it to bind to the operator site
  2. Most proteins involved with lactose ulitization are degraded
46
Q

The mutant strain _______ results in constitutive expression (constant expression) of the lac operon whether lactose is presence or absent

A

lacl-

47
Q

The ______ results in expression of the operon even when lactose is absent because the loss-of-function mutation in the lacl gene prevents the lac repressor from binding to the lac operator site & inhibiting transcription

A

lacl-

48
Q

Merozygote strain

A

Contains the lacl- mutant strain on the chromosome & a normal lacl gene on the plasmid

49
Q

What are the two hypotheses for lacl function?

A
  1. lacl is a repressor that is active without lactose & lacl- mutant is an inactive repressor (to yield constitutive operon)(Hypothesis 1)
  2. lacl is an activator that is inactive without lactose & lacl- mutant is a constitutive activator (constitutive operon) (hypothesis 2)
50
Q

In catabolite repression when only lactose is present, cAMP levels are ______ & the cAMP binds to CAP site. A domain in the CAP interacts with RNA polymerase which cause it to bind to the promoter. In the presence of lactose, the lac repressor is not bound to the operator site is transcription can occur at a ______ rate

A

High, high

51
Q

In catabolite repression in the absence of both lactose & glucose, cAMP levels are _____ but the binding of the lac repressor inhibits transcription even though CAP is bound to the DNA so therefore the transcription rate is ______

A

High, low

52
Q

The presence of lactose in catabolite repression causes the lac repressor to be inactive which prevents it from binding to the operator site. However when glucose is presence decreases cAMP levels so its released from CAP which causes CAP not to bind to CAP site so the transcription of the lac operon is _______ when both sugars are present

A

Low

53
Q

When only glucose is presence in catabolite repression the transcription of the lac operon is _______ because the lac repressor is bound to the operator site & CAP is not bound to the CAP site

A

Low

54
Q

CAP is an _______

A

Activator

55
Q

cAMP is an ________

A

Inducer

Biology (64 decks)

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