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genetics > chapter 13 part 1 > Flashcards

chapter 13 part 1 Flashcards

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1
Q

what do activator proteins bind & how do they affect transcription

A

bind regulatory sequences to stimulate transcription

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2
Q

what do repressor proteins bind & how do they affect transcription

A

bind other (so not regulatory ones)
sequences to hinder transcription

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3
Q

where are regulatory proteins often found?

A

in large complexes in eukaryotes
-unlike in bacteria, one transcription factor may regulate tens to hundreds of target genes

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4
Q

what are the three regulatory DNA sequences

A
  1. core promoter region
  2. proximal elements
  3. enhancer/silencer sequences
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5
Q

about the core promoter region!

A

it contains the TATA Box & other sequences
it is immediately adjacent to the start of transcription
-binds RNA pol II & its associated general transcription factors (GTFs)

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6
Q

tell me about proximal elements!

A

they are located upstream of the core promoter region & bind additional regulatory proteins

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7
Q

tell me about enhancer/silencer sequences!

A

they act from greater distances from the core promoter
-the bind regulatory proteins that interact with proteins bound to one another
-enhancers/silencers can be located upstream, downstream, close to, or very far, or even within the genes they regulate

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8
Q

where can enhancers/silencer sequences

A

can be located upstream, downstream, close to, or very far, or even within the genes they regulate

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9
Q

all three regulatory regions contain ____-_______ regulatory sequences

A

cis acting
they regulate transcription of genes on the same chromosome as the sequence

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10
Q

what binds the core promoter & are they cis or trans acting?

A

RNA pol II & various general transcription factors (GTFs)
-trans-acting regulatory proteins which can bind to their target sequence on any chromosome

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11
Q

what are enhanceosomes

A

when there are aggregations of multiple proteins from large complexes at enhancers

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12
Q

what does the enhanceosome direct

A

DNA bending/loop formation that allow enhanceosome proteins to interact with RNA pol & transcription factors at the core promoter & proximal promoter elements

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13
Q

what does enhancer activity typically help control

A

the timing & location of gene transcription

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14
Q

SV80 enhancer

A

consists of seven adjacent regions that are about 200 bp upstream of the transcription start point
each segment binds specific regulatory proteins

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15
Q

Enhancers and silencers typically contain ___________ _____ (modules) for several transcription factors

A

binding sites

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16
Q

what are modules

A

binding sites

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17
Q

what do modules allow silencers/enhancers to do?

A

integrate activities of different transcription factors to produce different outputs

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18
Q

what are pioneer factors?

A

are the first to bind regulatory molecules, facilitating the binding of additional transcription factors

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19
Q

can the same sequence act as an enhancer or a silencer?

A

yes! depending on which regulatory proteins are present & bind to the sequence (often cell type specific)

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20
Q

what is SHH

A

sonic hedgehog gene

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21
Q

what does SHH gene do?

A

directs limb formage & is controlled by an enhancer 1 million base pairs away from SHH gene

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22
Q

what type of fashion is SHH expressed in?

A

tissue-specific due to the action of two different enhancers

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23
Q

what does LCR stand for?

A

locus control region

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24
Q

what does LCR do?

A

it is a highly specialized enhancer that regulates transcription of multiple genes packaged into complexes of closely related genes

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25
Q

how many sequences does the LCR regulating the beta-globin complex contain & what are they?

A

4
HS1, HS2, HS3, HS4

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26
Q

what do the four distinct sequences regulating beta globin work together to do?

A

produce the correct expression of each type of beta-globin gene throughout development

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27
Q

how does the LCR function

A

by recruiting the chromatin-modifying, coactivator, & transcription complexes

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28
Q

what do HS1 & HS2 do?

A

they bind regulatory proteins that direct formation of small DNA loops & recruitment of additional factors

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29
Q

muations in the sigma- & beta-globin genes produce hereditary anemias called what

A

thalassemia

30
Q

can some thalassemia patients have no discernible muations?

A

yes, some may have no discernible mutations in the protein-coding part of the globin genes, nor in their promoters

31
Q

what are some thalassemia cases due to?

A

deletions that alterd the LCR region, causing abnormal expression of the globin genes

32
Q

what is UAS

A

yeat upstream activator sequences

33
Q

in the yeast Saccharomyces cerevisiae, transcription of genes in what pathway are carefully refulated by enhancer-like sequences

A

galactose utilization pathway

34
Q

what happens in the UAS when galactose is the only sugar available?

A

wild-type yeast induce transcription of four enzyme-producing genes
GAL1, GAL2, GAL7, GAL 10

35
Q

what are the four enzyme producing genes in UAS & what do they do?

A

GAL1, GAL2, GAL7, GAL10
they import and break down galactose

36
Q

do each of the GAL genes have their own promote and similar enhancer like sequencesr?

A

yes

37
Q

what are the GAL genes bound by?

A

Gal4

38
Q

what is Gal4 encodes by?

A

GAL4 gene

39
Q

is Gal4 sometime are always present in cells?

A

always
it is continuously present in cells

40
Q

what is the enhancer like element

A

upstream activator sequence
UAS of UASg

41
Q

what happens to Gal4 in the absence of Galactose

A

Gal4 is bound & inactivated by Gal80

42
Q

what is Gal4 like?

A

an enhancer like sequence

43
Q

things about UASG (how many, how many bp, binding site for what)

A

UASg element contains two 17 bp repeat sequences that are binding sites for Gal4

44
Q

what does Gal4 function as?

A

a homodimer

45
Q

what happens when Gal80 is bound to Gal4 (when galactose is absent)

A

the Gal4 DNA-binding domain is unable to bind to UASG

46
Q

what binds to Gal80 when galactose is present?

A

galactose & Gal3 bind to Gal80

47
Q

what is Gal3 encoded by?

A

the GAL3 gene

48
Q

what happens when galactose is present

A

-galactose & Gal3 bind to Gal80
-Gal80 releases Gal4- freeing the DNA-binding domain of Gal4 to recognize & bind to the UASG sites
-the transcriptional activation domain of Gal4 homodimer then activates transcription of GAL genes

49
Q

what activates transcription of the GAL genes

A

transcriptional activation of the Gal4 homodimer when it binds to UASG sites

50
Q

what leads to formation of a mediator

A

when Gal4 binds UASG

51
Q

what is a mediator

A

a multiprotein complex
an enhaceosome that induces formation of a DNA loop, contacting the general transcription apparatus at the GAL gene promoters

52
Q

what allows the transcription factors to bind?

A

physical changes in the DNA

53
Q

what does physical distortion of the DNA allow?

A

it allows UASG promoter to bring this sequence into contact with the promoter & RNA pol II to initiate transcription

-UASG is NOT a proximal promoter; it is further upstream

54
Q

do eukaryotic repressors & bacteria repressors inhibit transcription through the same mechanisms?

A

no- eukaryotic repressors do it differently

55
Q

what is one mechanism of binding repressor proteins?

A

through silencer sequences that directly prevent enhancer-mediated transcription

56
Q

what do silencer sequences do

A

they directly prevent enhancer-mediated transcription

57
Q

are silencer sequences cis or trans acting?

A

they are cis-acting

58
Q

what genes utilize silencer sequences?

A

GAL genes

59
Q

what binds the silencer sequences upstream of the GAL genes?

A

protein Mig1 is produced in the presence of glucose & binds the silencer sequence

60
Q

is Mig1 produced in the presence or absence of glucose?

A

in the presence

61
Q

where are the silencer sequences of GAL genes located?

A

located between the UASG sequences & the promoters

62
Q

what protein does Mig1 attract?

A

Tup1 & the two together form a repressor complex that prevents UASG from initiating transcription

63
Q

what prevents UASG from initiating transcription?

A

when Mig1 attracts Tup1 & they form a repressor complex

64
Q

what are insulator sequences?

A

they are cis-acting sequences located between enhancers & the promoters of genes that need to be protected from the action of the enhancers

65
Q

what do insulators ensure?

A

there is only the target gene is regulated by the enhancer

66
Q

what may insulators allow?

A

DNA loops that contain the enhancers & their intended target promoters while excluding non-target genes

67
Q

what do DNA loops exclude?

A

non-target genes

68
Q

Some insulator sequences function by containing the spread of ________________.

A

heterochromatin

69
Q

what is constitutive heterochromatin

A

when regions of the genome are always heterochromatic

70
Q

facultative heterochromatin

A

regions that switch between euchromatin & heterochromatin often based on tissue type or cellular needs during certain times

71
Q

when does positron effect variegation occur?

A

(PEV) occurs when the euchromatin is placed (by mutation) neat heterochromtain, which can then spread converting some of the euchromatin or heterochromatin, this can silence genes

72
Q

when euchromatin is converted into heterochromatin, when can occur to genes?

A

it can silence them

genetics (37 decks)

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