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Flashcards in e x a m IV Deck (74):
1

negative control

gene transcription is actively repressed

2

with repressor:

no transcription

3

without repressor:

transcrption

4

positive control

gene transcription is induced

5

with activator protein

transcription

6

without activator protein

no transcription

7

effector molecule

regulates the function of activators and repressors

8

with effector bound to repressor:

transcription

9

without effector bound to repressor:

no transcription

10

what does effector to do to repressor protein

changes confirmation

11

with effector bound to activator:

translation

12

without effector bound to activator:

no translation

13

allosteric effector

binds to the allosteric site of regulatory protein leading to conformational change

14

effector present in activator site

protein binds to binding (allosteric site)

15

effector present in repressor site

effector causes protein to be removed from active binding site

16

permease

transports lactose into cell
(permeate)

17

beta-galactosidase

cleaves lactose to produce galactose & glucose

18

the lac system is used in...

prokaryotes

19

what induces the synthesis of beta-galactosidase and permease?

addition of certain sugars
- glucose
- lactose

20

how many promotors are there for multiple genes in prokaryotes?

ONE

21

I gene codes for

repressor protein

22

repressor protein controls...

responsiveness to lactose

23

what does lactose do?

binds to repressor protein
removes repressor from DNA
lac Z and lac Y gene are expressed

24

I- mutant

defective repressor protein
causes operon to be ON all the time
continuous mRNA transcription

25

Is (supressor) mutant

suppression of gene expression
lactose can no longer bind to repressor
galactosidase or permease are NEVER expressed

26

Operator

specific region downstream from promotor
DNA sequence that the repressor binds to

27

Oc mutant

causes repressor protein to not be able to bind to operator
b-galactosidase & permease are ALWAYS ON

28

lac promoter

physically blocks RNA polymerase from working
(stop sign in front of operator)

29

two consensus sequences for efficient RNA polymerase binding in prokaryotes

-35 region
pribnow box (-10 base pairs)

30

lac operon is shut down when...

lactose is not present

31

POZY

promoter
operon
lac z gene
lac y gene

32

glucose blocks the induction of lactose metabolism...

because glucose is more energetically favorable
glucose is processed first over lactose

33

adenylate cyclase produces

cAMP

34

what does cAMP bind to

CAP
(catabolic activator protein)

35

what does cAMP-CAP do?

binds promotor and facilitates RNA polymerase bind and transcription initiation
STABILIZES the protein

36

what does glucose do to the lac system?

glucose metabolite block activity of adenylate cyclase
ATP--> cAMP conversion is shut down
cAMP-CAP complex is not formed
no expression of lac operon

37

cis regulatory element

in the same segment of DNA as the gene of interest

38

trans regulatory element

factors produced by other genes that act on the gene of interest
not located in the same spot of the bacterial chromosome

39

trp operon

controlled by 5 biosynthetic genes
encoded for within a single operon

40

how is trp operon regulated

tryptophan levels

41

primary control of trp protein

trp repressor binds tryptophan and turn off the operon when tryptophan levels are adequate
binds to operator to block RNA polymerase movement
aka: on/off switch due to adequate levels of tryptophan

42

secondary control of trp protein

stem & loop folding to ensure used to either terminate
loop forms when in excess of tryptophan

43

when high tryptophan

stem & loop form
termination of transcription

44

when low tryptophan

ribosome is stalled at trp codons
transcription continues

45

why gene reg is more complicated in eukaryotes than prokaryotes:

each gene is separately controlled by a single promoter
numerous proteins contribute to gene reg
multiple DNA switches
ground state is OFF

46

what is required for binding RNA polymerase to eukaryotic promoters?

GC-rich box
CAAT box
TATA box

47

changing promotor sequences will lead to...

dramatic reduction of transcription

48

general transcription factors

recruit RNA polymerase II to TATA box

49

specific transcription factors

directly bind to DNA to influence transcription of target genes
help or hinder pre-initiation complex
stabilize RNA polymerase binding

50

why is DNA looped?

it is exposed to more activators, enhancer sites, repressors
all helps with stability

51

what is DNA binding domain needed for?

specific transcription factors to bind to enhancer/silencer DNA sequence

52

activation domain

needed to interact with proteins bound to promoter to speed up / slow down transcription

53

GAL-4

yeast transcription factor for lactose metabolism

54

what regulatory gene is lac-z linked to?

GAL-4

55

synergism

interaction between two factors; combined effect is greater than the SUM of the two

56

nitric oxide synthetase

makes NO in cells

57

what happens when interferon gamma & LPS act alone

little or no increase in NOS

58

what happens when interferon gamma & LPS work together?

LARGE increases in NOS mRNA

59

heterochromatin

darkly stained regions of the chromosome
some gene expression

60

euchromatin

lightly stained regions
main site of gene expression

61

nucleosome

8 separate proteins
multiple coiled on top of each other
fit inside nucleus

62

histones

group of proteins that packages DNA into chromatin

63

function of chromatin remodeling

displace nucleosomes to allow transcription factors to bind to DNA regulatory regions

64

SWI-SNF protein

moves nucleosomes out of the way

65

histone acetyltransferase (HAT)

adds acetyl group to histone tails

66

histone deacetyltransferase (HDAT)

removes acetyl groups from histones
--> decreased transcription

67

beta-inferon

encodes antiviral protein inferno
is activated at high levels with viral infection

68

enhanceosome

moves nucleosomes out of the way for access to TATA box

69

GCN5

coactivator protein that acetylates nucleosome

70

CBP protein

coactivator with histone acetylase activity
recruits RNA polymerase II

71

epigenetics

study of inherited changes in gene expression without a change in the underlying DNA sequence

72

epigenetics is...

the inheritance of HOW the gene is expressed not WHAT genes are expressed

73

silencing is generated in DNA methylation without...

any change in the DNA sequence

74

what happens to one of the X chromosomes in females?

inactivated through methylation so double the genes aren't expressed