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genetics > chapter 12 part 1 > Flashcards

chapter 12 part 1 Flashcards

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Biology 101 flashcards
1
Q

constitutive transcription

A

occurs for genes needed continuously to perform housekeeping tasks, needed for life of the cell

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2
Q

regulated transcription/inducible genes

A

for genes only needed for responses to changing environmental conditions or during certain phases of growth

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3
Q

what does regulated transcription include the control of

A

imitation and amount of transcription

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4
Q

what is the major means of regulating gene expression bacteria

A

transcriptional regulation

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5
Q

what mechanisms are also important for gene expression

A

post-transcriptional mechanisms

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6
Q

negative control of transcription

A

involves binding of a repressor protein to a regulatory DNA sequence and preventing transcription

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7
Q

where do repressors bind

A

operators through DNA-binding domain

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8
Q

does negative control turn on or off genes

A

both

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9
Q

positive control of transcription

A

involves binding of an activator protein to regulatory DNA and initiating gene transcription

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10
Q

binding of activator to DNA causes what?

A

RNA polymerase to initiate transcription

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11
Q

does positive control turn on or off genes

A

both

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12
Q

what 2 domains do activator/repressor proteins have?

A
  • DNA binding domain
  • allosteric domain
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13
Q

activator and repressor proteins are examples of what?

A

transcription factors

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14
Q

DNA-binding domain

A

locates and binds operator DNA sequence or other target DNA sequences

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15
Q

allosteric domain

A

binds a molecule or protein, which causes a change in conformation of the DNA-binding domain, altering its function

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16
Q

allostery

A

to turn DNA binding function on or off

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17
Q

4 categories of gene regulation

A
  1. negative inducible
  2. negative repressible
  3. positive inducible
  4. positive repressible
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18
Q

inducible

A

the effector molecule causes transcription to start

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19
Q

repressible

A

the effect molecule causes transcription to stop

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20
Q

all 4 categories of gene regulation require the participation of an additional…

A

allosteric effector/inducer/inhibitor/corepressor moelcule

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21
Q

negative inducible

A
  • TF = repressor
  • binding of effector molecule to TF causes transcription to start
  • effector molecule is inducer
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22
Q

ex. of negative inducible

A

Lac operon

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23
Q

negative repressible

A
  • TF = repressor
  • binding of effector molecule to TF causes transcription to stop
  • effector molecule is co-repressor
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24
Q

ex. of negative repressible

A

Trp operon

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25
Q

positive inducible

A
  • TF = activator
  • binding of effector molecule to TF causes transcription to start (co-activator)
  • effector molecule is inducer
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26
Q

positive repressible

A
  • TF = activator
  • binding of effector molecule to TF causes transcription to stop
  • effector molecule is inhibitor
27
Q

bacterial regulatory DNA sequences frequently have what?

A

inverted or direct repeats

28
Q

each polypeptide of a regulatory homodimer interacts with what?

A

one repeat

29
Q

most common structural feature of homodimer (repeat) proteins in bacteria

A

helix-turn-helix motif (HTH)

30
Q

helix-turn-helix (HTH) motif

A

two a-helical regions interact with the DNA sequences

31
Q

a recognition and a stabilizing helix are separated by a ________ in each polypeptide

A

turn

32
Q

operon

A

clusters of genes undergoing coordinated transcriptional regulation by a shared regulatory region

33
Q

where are operons commonly found?

A

bacterial genomes

34
Q

genes in an operon nearly always participate in what?

A

the same metabolic or biosynthetic pathway

35
Q

can an operon be activated or repressed

A

both

36
Q

switching between activated/repressed are typically responsive to what?

A

environmental cues

37
Q

how many proteins does the lactose (lac) operon of E. coli produce

A

3 - all needed for use of lactose

38
Q

what is the main energy source for E. coli and most organisms

A

glucose

39
Q

what is glucose metabolized by

A

glycolysis pathway

40
Q

lactose

A

one of many sugars that can serve as an alternate carbon source
- utilization controlled by lac operon

41
Q

lactose is a disaccharide of __________ and __________

A

glucose and galactose

42
Q

in lactose, what are glucose and galactose joined by

A

covalent B-galactoside linkage

43
Q

bacteria with a lac- phenotype can grow on media containing what?

A

lactose as the only sugar

44
Q

can bacteria with the lac- phenotype utilize lactose?

A

no

45
Q

how can lac- bacteria grow on lactose

A

produce gated channel (permease) at cell membrane that allows lactose to enter the cell and the enzyme B-galactosidase to break the B-galactoside linkage

46
Q

glucose produced by lactose breakdown enters _________

A

glycolysis

47
Q

galactose is processed to produce _________

A

glucose

48
Q

the breakdown of lactose produces a small amount of _________

A

allolactose

49
Q

what does allolactose act as

A

inducer compound

50
Q

3 binding sites of lac regulatory region

A
  1. promoter - binds RNA polymerase
  2. operator - binds lac repressor protein
  3. CAP binding site
51
Q

3 operon structural genes of lac

A
  1. lac Z
  2. lac Y
  3. lac A
52
Q

what does lacZ encode

A

B-galactosidase
- cleaves lactose into glucose and galactose

53
Q

what does lacY encode

A

permease
- helps transport lactose into the cell

54
Q

what does lacA encode

A

transacetylase
- precise function is mystery

55
Q

how are lac Z, Y, and A transcribed

A

as single, polycistronic mRNA, which is translated to produce the 3 distinct polypeptides

56
Q

what gene is next to the lac operon?

A

lacI

57
Q

is lacI part of the lac operon?

A

no

58
Q

is lacI constitutively or inducible expressed

A

constitutively

59
Q

what does lacI encode

A

the lac repressor protein

60
Q

lac repressor protein

A
  • homo-tetramer
  • DNA-binding domain that binds to the lacO sequence (operator)
  • has allosteric domain that binds to the inducer (allolactose)
61
Q

what is present even when lactose is absent?

A

a very low basal level of transcriptional from the operon

62
Q

how is there always a small amount of transcription for the lac operon

A

small amount of permeate and B-galactosidase proteins allow for the import of lactose into a cell and production of allolactose

63
Q

what happens when there are no or low levels of B-galactosidase

A

no allolactose in the cell, lac repressor protein binds to lacO and prevents transcription

genetics (37 decks)

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