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General Bio I > Chapter 18 (Genetic Regulation) > Flashcards

Chapter 18 (Genetic Regulation) Flashcards

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Biology 101 flashcards
1
Q

Why do cells need gene regulation?

A

all genes can’t be expressed at the same time

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2
Q

When are genes expressed in a cell?

A

When a cell needs it for the work that has to be done at any given moment

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3
Q

Gene expression is altered in response to what?

A

any change in the environment

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4
Q

Which are more responsive to their environment, single-celled organisms or multi-celled organisms and why?

A

single-celled organisms (prokaryotes) because they have to focus on internal and external environments

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5
Q

What does gene regulation affect in multi-celled organisms in many steps?

A

development, cell differentiation, internal environments

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6
Q

What can genes do to enzymes?

A

stop their formation so that there is potential for an enzymatic pathway to be shut down

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7
Q

What are operons?

A

a genetic regulatory system in PROKARYOTES

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8
Q

Where can operons be found?

A

in bacterial/prokaryotic cells ONLY

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9
Q

Why did the operon system get developed in the first place?

A

structure of the genome in a prokaryotic cell, the genes are located in a given area (packed together)

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10
Q

What are the components of operons?

A

operators and repressors

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11
Q

What are operators?

A

highly conserved series of nucleotides (DNA-based) where the repressor protein binds in order to block RNA polymerase from working

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12
Q

Where are operators found?

A

after the promoter region of the gene in question

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13
Q

What are promotors regions?

A

portions on transcription starting sites that regulate the initiation transcription of the gene by controlling where RNA polymerase binds

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14
Q

What does the repressor protein do?

A

represses gene transcription (turns off operon)

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15
Q

What is the repressor protein?

A

the gene product of a separate regulatory gene (transcribed first at 5, upstream)

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16
Q

Where is the repressor protein gene located?

A

5’ end, upstream

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17
Q

How does the repressor protein inhibit the operon?

A

binds to the operator and inhibits RNA polymerase

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18
Q

By what process is the repressor protein regulated?

A

allosterically (active or inactive)

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19
Q

How is the repressor protein regulated?

A

a corepressor activates the repressor protein and an inducer inhibits the repressor protein

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20
Q

What are the types of operons?

A

inducible and repressible

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21
Q

What kind of gene regulation are the two operons?

A

negative gene regulation

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22
Q

What is gene regulation?

A

ability to stop gene transcription (flipping switch off)

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23
Q

Is the inducible operon active or inactive?

A

inactive

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24
Q

What does the activity of the inducible operon rely on?

A

the activity level of the repressor protein

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25
Q

What happens in an inducible operon?

A

binding of inducer inactivates the repressor and turns on transcription

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26
Q

Is the repressor protein naturally active or inactive?

A

inactive

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27
Q

What is the inducible operon used for?

A

catabolic needs

28
Q

Are repressible operons on or off?

A

on most of the time

29
Q

What happens in the repressible operons?

A

binding of a repressor to the operator shuts off transcription

30
Q

What do cells utilize repressible operon for?

A

anabolic needs (stuff that is made all the time but is made a little too much at a certain time)

31
Q

What is an example of a repressible operon?

A

trp operon

32
Q

What is tryptophan?

A

amino acid for growth

33
Q

Are tryp genes on or off most of the time?

A

on because the cell needs the tryptophan amino acid

34
Q

Is the repressor for trp operon off or on?

A

can be in the inactive or active form

35
Q

What is the corepressor for tryptophan production?

A

tryptophan itself (like feedback inhibition)

36
Q

When is the trp operon turned off?

A

when there is too much tryptophan in the cell

37
Q

What is an example of inducible operons?

A

lactose operon

38
Q

What is lactose?

A

sugar source that is not always available to the cell

39
Q

What do lac operon genes code for?

A

enzymes that hydrolyze lactose

40
Q

Is the lac operon usually off or on?

A

repressed and no enzymes made until the presence of allolactose

41
Q

Is the lac repressor protein active or inactive most of the time?

A

active

42
Q

What activates the repressor protein in the lac operon?

A

allolactose

43
Q

What kind of regulation can the lac operon do?

A

positive and negative regulation

44
Q

How can the lac operon have positive regulation?

A

making more of operons so more enzymes are made to break down lactose

45
Q

What is RNA polymerase?

A

needed to start transcription

46
Q

What is a promotor?

A

the sequence of DNA that RNA polymerase binds (acts like a primer)

47
Q

What is the trp operon essential for?

A

production of tryptophan

48
Q

Where is trp operon located?

A

on e. coli bacteria in the intestines

49
Q

Where does the RNA polymerase bind?

A

promotor region

50
Q

What does the e.coli bacteria need?

A

tryptophan

51
Q

What happens in the trp operon if there is low tryptophan?

A

the repressor protein isn’t bound to the operator and allows RNA polymerase to transcribe the mRNA for tryptophan (inactive)

52
Q

What happens in the trp operon if there is too high of tryptophan?

A

tryptophan acts as a corepressor and binds to detached repressor protein, the complex then binds to operon to block RNA polymerase (active), feedback inhibition-like

53
Q

What kind of operon is the lac operon?

A

inducible operon

54
Q

What does the lac operon code for?

A

enzymes involved in breaking down lactose (sugar)

55
Q

What does the lac operon do if there is no lactose?

A

repressor protein bound to lac operator to prevent any breakdown of lactose by blocking RNA polymerase

56
Q

What does the lac operon do if there is too much lactose?

A

allolactose (isomer of lactose) acts as inducer and binds to repressor protein and detatches the complex from operator for RNA polymerase to start

57
Q

What happens to the lac operon if there is little glucose and lactose?

A

allolactose binds to repressor protein to induce lac operon and cap protein binds to cap site to further enhance activation/transcription to break down lactose

58
Q

What happens to lac operon if there is more glucose and more lactose?

A

allolactose binds to repressor protein to induce RNA polymerase to transcribe, but cap protein doesn’t bind to cap site so LESS transcription

59
Q

What are transcription factors?

A

proteins found at operon that bind to a site on DNA to activate transcription

60
Q

What do transcription factors rely on?

A

RNA polymerase

61
Q

What are activators?

A

found at promotor region that increases transcription (ex: CAP)

62
Q

All cells have what type of genome?

A

the same type of genome, but depends on what gene is activated or not

63
Q

What is gene silencing?

A

genes switched off where only small fraction of DNA codes for proteins

64
Q

What does microRNA do?

A

single-stranded RNA molecules that can bind to mRNA to turn off genes

65
Q

How is miRNA made?

A

dicer protein chops up the primary transcript of double-stranded RNA and splits into 1 strand

66
Q

How is RISC complex made?

A

RISC complex picks up miRNA pieces

67
Q

What does the RISC complex do?

A

slices single-stranded RNA to make it stop producing amino acids

General Bio I (18 decks)

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