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Genetics > Chapter 16: Control of Gene Expression in Prokaryotes > Flashcards

Chapter 16: Control of Gene Expression in Prokaryotes Flashcards

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Biology 101 flashcards
1
Q

Structural Genes

A

encoding proteins that “make or break”

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2
Q

Regulatory Genes

A

encoding products that interact with other sequences and affect the transcription and translation of these sequences

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3
Q

Regulatory Elements

A

DNA sequences that are not transcribed but play a role in regulating other nucleotide sequences

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4
Q

What makes expression constituitive?

A

if a gene is continuously expressed under normal cellular conditions

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5
Q

If a cell is undergoing catabolite repression, what kind of control is it undergoing?

A

Positive

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6
Q

What type of positive control uses CAP, cAMP, and glucose to repress the metabolism of other sugars?

A

Catabolite repression

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7
Q

Where do CAP and cAMP bind?

A

slightly upstream of the lac gene promoter

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8
Q

What is inversely proportional to the level of available glucose?

A

cAMP

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9
Q

What is positive control?

A

-stimulate gene expression by using a regulatory protein is an activator
-has to be turned on

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10
Q

How does catabolite repression function when glucose is low?

A

-levels of cAMP are high and it readily binds to CAP. ONce binded to the DNA, DNA polymerase increases binding efficiency
-RESULTS: high rates of transcription and translation of structural genes AND the production of glucose from lactose

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11
Q

How does catabolite repression function when glucose is high?

A

levels of cAMP are low and less likely to bind to CAP. RNA polymerase cannot bind as efficiently so transcription is low

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12
Q

What is negative gene expression?

A

-needs to be turned off
-inhibit gene expression; regulatory protein is a repressor

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13
Q

What stage are most proteins regulated in?

A

transcription

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14
Q

What are the different shapes within a protein?

A

domains

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15
Q

What is significant about the domains of a protein?

A

~60-90 amino acids that are responsible for binding to DNA and forms hydrogen bonds

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16
Q

What is the specific shape that is found within a domain?

A

motif

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17
Q

What is significant about motifs?

A

a simple structure that fits into the major groove of the DNA

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18
Q

What is a helix-turn-helix motif?

A

-regulatory in prokaryotes
-contains a DNA-binding helix, turn, then a dimer binding helix

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19
Q

What is the signifigance of a zinc finger motif?

A

eukaryotic regulation

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20
Q

What is the signifigance of a leucine zipper motif?

A

eukaryotic regulation

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21
Q

What is an operon?

A

group of genes sharing a common promoter and are transcribed as a unit

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22
Q

What is a promoter+ additional sequences that control transcription (operator)+ structural genes?

A

operon

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23
Q

Are operons more common in prokaryotes or eukaryotes?

A

typical in prokaryotes but not in eukaryotes

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24
Q

How were operons discovered?

A

found by investigating decision of E.coli to eat glucose or lactose

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25
Q

What is a regulator gene?

A

DNA sequence that encodes products that affect the operon function, but are not part of the operon

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26
Q

How can regulator genes regulate transcription of mRNA?

A

regulator genes must have their own promoter that encodes for a regulatory protein. It must then bind to the operator site

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27
Q

What type of operon has transcription off and needs to have it turned on?

A

inducible operons

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28
Q

What type of operon has transcription turned on and needs it be turned off?

A

repressible operon

29
Q

What is the function of the lac operon?

A

it is a negative, inducible operon that functions in lactose metabolism

30
Q

What is the inducer in the lac operon?

A

allolactose

31
Q

lacI

A

repressor encoding gene

32
Q

lacP

A

operon promoter

33
Q

What is contained in the lacP?

A

-35 and -10 consensus sequences

34
Q

lacO

A

operon operator

35
Q

lacZ

A

encoding B-galactosidase

36
Q

lacY

A

encoding permease

37
Q

What is the function of permease?

A

actively transprots lactose into the cell where B-galactosidase breaks it into galactose and glucose

38
Q

What is the function of B-galactosidase?

A

-breaks lactose into glactose and glucose and the related compound of allolactose (to then be converted to galactose and glucose)

39
Q

lacA

A

encoding transacetylase

40
Q

Does the repression of the lac operon completely shut down transcription?

A

no

41
Q

How does the regulatory protein function in the absence of lactose?

A

the repressor binds to the operator and inhibits transcription

42
Q

What does it mean that the lacI+ gene is transdominant?

A

the repressor produced can bind to both operartors and repress transcription in the anbsence of lactose

43
Q

How does the regulator protein function in the prescence of lactose?

A

some of the lactose is converted to allolactose. This binds to the regulator protein making it inactive

44
Q

What happens to the structrual genes of of the lac operon in the prescence of lactose?

A

they are transcribed and translated since the regulator cannot bind to the operator

45
Q

When is functional B-galactosidase produced from the lacZ+ gene?

A

when lactose is present and it has inactivated the repressor

46
Q

What does the lacI gene produce in the prescence of lactose?

A

a super repressor that does not bind lactose and is transdominant

47
Q

What is a partial diploid?

A

full bacterial chromosome+ an extra piece of DNA on F plasmid

48
Q

How does the partial diploid function in the absence of lactose?

A

active represssor binds to the operator which creates B-galatosidase

49
Q

How does the partial diploid function in the prescence of lactose?

A

lactose binds to the repressor, which inactivates it and produces nonfunctional B-galactosidase

50
Q

What affects the structure of the enzymes but not the regualtion of their synthesis?

A

structural gene mutations

51
Q

Where do structural gene mutations occur and affect?

A

only affect lacZ or lacY and only occur on lacZ/lacY

52
Q

What affects the transcription of trans structrual genes?

A

regulator gene mutations

53
Q

What gene leads to constitutive transcription of three structural genes?

A

lacI-

54
Q

What is dominant over lacI- and is trans acting?

A

lacI+ is dominant and a single copy brings about normal regulation of lac operon

55
Q

What do operator mutations affect?

A

affect transcription of structural genes; cis

56
Q

Is an operator mutation dominant or recessive?

A

dominant over lacO+

57
Q

What do promoter mutations affect?

A

transcription of structural genes

58
Q

What is the trp operon?

A

a negative repressible operon that is composed of 5 structural genes

59
Q

What works together to convert chorismate to trytophan?

A

-the 5 structural genes
-trpE, trpD, trpC, trpB, and trpA

60
Q

How does the trp operon function when trp is low?

A

the trp repressor is noramlly inactive and cannot bind to the operator so transcription occurs

61
Q

How does the trp operon function when trp is high?

A

trp binds to the repressor and activates it. The repressor then binds to the operator and shuts transcription off

62
Q

What affects the continuation of transcription, not its initiation?

A

attenuation

63
Q

What action terminates transcription before it reaches the structural genes?

A

attenuation

64
Q

How does attenuation work in the trp operon when trp is high?

A

region 1 binds to region 2, which causes the binding of region 3 and 4
-premature transcription termination

65
Q

How does attenuation work in the trp operon when trp is low?

A

region 2 pairs with region 3 and termination does not occur in transcription

66
Q

Antisense RNA

A

complementary to targeted partial sequence of mRNA; they function by going to influence translation somewhere else

67
Q

Riboswitches

A

molecules influence the fomration of secondary structures in mRNA; RNA that has to bind to an RNA molecule to allow it to be linear and disrupt base pairing to prevent translation

68
Q

Ribozymes

A

mRNA molecules with catalytic activity

Genetics (12 decks)

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