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Bio 130 > Chapter 23 > Flashcards

Chapter 23 Flashcards

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Biology 101 flashcards
1
Q

Constitutive Genes

A

genes that are always on in every cell (important for regular cell functions)

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2
Q

Regulated Genes

A

get switched on and off based on what the cell needs

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3
Q

negative control

A

regulatory proteins stop transcription

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4
Q

positive control

A

regulatory proteins turn on transcription

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5
Q

operons

A

groups of genes with related functions driven by a single promoter; meaning one segment of DNA turns on the function in a cell

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6
Q

Inducible genes

A

genes are mostly off, and turned on when needed

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7
Q

which pathways are mostly inducible and which repressible

A 
catabolic = inducible
anabolic = repressible
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8
Q

repressible genes

A

genes mostly on and turned off when needs are met

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9
Q

5 levels of eukaryotic control

A

genomic, transcription, RNA processing and export, translation, and posttranslational

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10
Q

The trp operon

A

controls tryptophan synthesis;

repressed when trp levels are high

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11
Q

how does tryptophan function in trp operon

A

when there is enough trp, it binds to the repressor and activates it to repress the operon. when more trp is needed, it is removed and synthesis resumes

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12
Q

what type of control and what type of operon is trp operon

A

negative control and repressible operon

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13
Q

what is the lac operon

A

the 3 genes involved in lactose metabolism

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14
Q

Lac I

A

expressed constitutively and binds to operator to prevent transcription

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15
Q

what happens when lactose is present

A

lactose binds to repressor and removes it

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16
Q

what happens when glucose and lactose are present

A

glucose is preferred so it will be metabolized first but the presence of lactose releases the repressor so some lactose will be metabolized

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17
Q

what is cyclic AMP’s role

A

it reflects glucose levels so when it gets high cAMP activates the lac operon by binding to the cAMP regulatory protein

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18
Q

function of CRP (cAMP regulatory protein)

A

recruits polymerase to the promotor which increases the transcribing of the lac genes

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19
Q

high glucose means

A

low cAMP levels

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20
Q

what type of control is cAMP/CRP complex

A

positive because it activates transcription

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21
Q

what type of control is the lac operon

A

negative because the repressor blocks the polymerase

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22
Q

what kind of operon is the lac operon

A

inducible because it is only turned on when lactose is available

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23
Q

3 kinds of genomic control

A

gene amplification, gene deletion, chromatin structure (histones and inaccessible DNA)

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24
Q

gene deletion

A

loss of genetic info (like RBC)

25
Q

gene amplification

A

copies of same gene

26
Q

the histone code regulation

A

addition of methyl, acetyl, and phosphate groups to histones which alters chromatin structure (can activate or repress genes)

27
Q

chromatin structure regulation that’s not histones

A

compact regions are inaccessible to transcription machinery (DNA methylation)

28
Q

barr bodies

A

inactivated X chr

29
Q

proximal control elements

A

binding sites for regulatory transcription factors that affect the initiation of transcription; located upstream but only 100-200 base pairs away from the promoter

30
Q

distal control elements

A

function either upstream or downstream from promoter at highly variable distances; either silencers or enhancers

31
Q

silencer

A

distal control element that inhibits transcription as a binding site for repressors

32
Q

enhancers

A

distal control element that stimulates transcription as the binding site for activator proteins

33
Q

transcription factor activation via phosphorylation

A
  1. CREB is bound to DNA near cAMP activated genes on the CRE
  2. cAMP facilitates phosphorylation of transcription factor CREB
  3. activated CREB recruits CBP which then remodels chromatin and recruits polymerase
34
Q

what is CREB

A

a transcription factor

35
Q

CBP

A

CREB-binding protein

36
Q

CRE

A

cAMP response element

37
Q

3 broad ways transcription is controlled

A

Proximal control elements, distal control elements, and mRNA is produced in different amounts in different cells

38
Q

in what ways does RNA processing and transport control gene expression

A

alternative splicing, alternative poly-A sites, and export is dependent on several factors being present

39
Q

what factors is RNA export dependent on

A

Proper processing (5’ cap and poly-A tail), or it may require a nuclear export signal

40
Q

ways translation is controlled (6)

A

initiation factors, phosphorylation of eIFs, control elements, mRNA stability, RNA interference, miroRNAs

41
Q

control elements

A

located in untranslated regions and regulate binding of transcription factors

42
Q

initiation of transcription requires

A

several initiation factors (eIFs)

43
Q

what does phosphorylation of eIFs result in

A

either activation or inactivation

44
Q

where is iron response element found (IRE) that increases transcription

A

5’ UTR of ferritin in mRNA

45
Q

how does IRE work without enough iron

A

IRE-binding protein binds to IRE in the absence of iron which represses translation

46
Q

what happens with IRE when there is enough iron

A

iron binds to IRE-binding protein to activate it and starts translation

47
Q

mRNA stability

A

if RNAs are around longer, they can make more proteins

48
Q

factors affecting mRNA stability

A

length of poly-A tail, half life ranges from 30 min - 10 hrs, control elements in UTRs

49
Q

mRNA stability example of IRE in 3’ UTR of transferriten receptor mRNA

A

iron binds to IRE-binding protein to inactivate it so the mRNA can be degraded; in the absence of iron, the IRE-binding protein binds to IRE which protects the mRNA from degradation

50
Q

RNA interference (RNAi)

A

uses dsRNAs to target specific mRNAs for degradation or translation inhibition

51
Q

RNAi pathway

A
  1. dsRNA is cleaved by Dicer into siRNAs
  2. siRNAs assembled into RISC and 1 strand is retained as the guide strand
  3. guide strand targets mRNA based on regions of homology
52
Q

perfect homology

A

RISC degrades mRNA and targets new mRNA

53
Q

imperfect homology

A

RISC remains bound and blocks ribosomes

54
Q

microRNAs

A

they fold into hairpin structures and mimic dsRNA then hop into the RNAi pathway

55
Q

3 kinds of posttranslational control

A

protein degradation, modification to protein structure and function, ubiquitin targets proteins for destruction

56
Q

ubiquitin targets proteins for destruction

A

short chains of ubiquitin are added to lysine residues of proteins; recognition of proteasomes results in protein destruction

57
Q

half-life of proteins

A

range from minutes to weeks

58
Q

importance of protein half-life

A

proteins with shorter half-lives can respond to change more quickly

Bio 130 (19 decks)

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