e x a m IV Flashcards
negative control
gene transcription is actively repressed
with repressor:
no transcription
without repressor:
transcrption
positive control
gene transcription is induced
with activator protein
transcription
without activator protein
no transcription
effector molecule
regulates the function of activators and repressors
with effector bound to repressor:
transcription
without effector bound to repressor:
no transcription
what does effector to do to repressor protein
changes confirmation
with effector bound to activator:
translation
without effector bound to activator:
no translation
allosteric effector
binds to the allosteric site of regulatory protein leading to conformational change
effector present in activator site
protein binds to binding (allosteric site)
effector present in repressor site
effector causes protein to be removed from active binding site
permease
transports lactose into cell
permeate
beta-galactosidase
cleaves lactose to produce galactose & glucose
the lac system is used in…
prokaryotes
what induces the synthesis of beta-galactosidase and permease?
addition of certain sugars
- glucose
- lactose
how many promotors are there for multiple genes in prokaryotes?
ONE
I gene codes for
repressor protein
repressor protein controls…
responsiveness to lactose
what does lactose do?
binds to repressor protein
removes repressor from DNA
lac Z and lac Y gene are expressed
I- mutant
defective repressor protein
causes operon to be ON all the time
continuous mRNA transcription
Is (supressor) mutant
suppression of gene expression
lactose can no longer bind to repressor
galactosidase or permease are NEVER expressed
Operator
specific region downstream from promotor
DNA sequence that the repressor binds to
Oc mutant
causes repressor protein to not be able to bind to operator
b-galactosidase & permease are ALWAYS ON
lac promoter
physically blocks RNA polymerase from working
stop sign in front of operator
two consensus sequences for efficient RNA polymerase binding in prokaryotes
-35 region pribnow box (-10 base pairs)
lac operon is shut down when…
lactose is not present
POZY
promoter
operon
lac z gene
lac y gene
glucose blocks the induction of lactose metabolism…
because glucose is more energetically favorable
glucose is processed first over lactose
adenylate cyclase produces
cAMP
what does cAMP bind to
CAP
catabolic activator protein
what does cAMP-CAP do?
binds promotor and facilitates RNA polymerase bind and transcription initiation
STABILIZES the protein
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
cis regulatory element
in the same segment of DNA as the gene of interest
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
trp operon
controlled by 5 biosynthetic genes
encoded for within a single operon
how is trp operon regulated
tryptophan levels
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
secondary control of trp protein
stem & loop folding to ensure used to either terminate
loop forms when in excess of tryptophan
when high tryptophan
stem & loop form
termination of transcription
when low tryptophan
ribosome is stalled at trp codons
transcription continues
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
what is required for binding RNA polymerase to eukaryotic promoters?
GC-rich box
CAAT box
TATA box
changing promotor sequences will lead to…
dramatic reduction of transcription
general transcription factors
recruit RNA polymerase II to TATA box
specific transcription factors
directly bind to DNA to influence transcription of target genes
help or hinder pre-initiation complex
stabilize RNA polymerase binding
why is DNA looped?
it is exposed to more activators, enhancer sites, repressors
all helps with stability
what is DNA binding domain needed for?
specific transcription factors to bind to enhancer/silencer DNA sequence
activation domain
needed to interact with proteins bound to promoter to speed up / slow down transcription
GAL-4
yeast transcription factor for lactose metabolism
what regulatory gene is lac-z linked to?
GAL-4
synergism
interaction between two factors; combined effect is greater than the SUM of the two
nitric oxide synthetase
makes NO in cells
what happens when interferon gamma & LPS act alone
little or no increase in NOS
what happens when interferon gamma & LPS work together?
LARGE increases in NOS mRNA
heterochromatin
darkly stained regions of the chromosome
some gene expression
euchromatin
lightly stained regions
main site of gene expression
nucleosome
8 separate proteins
multiple coiled on top of each other
fit inside nucleus
histones
group of proteins that packages DNA into chromatin
function of chromatin remodeling
displace nucleosomes to allow transcription factors to bind to DNA regulatory regions
SWI-SNF protein
moves nucleosomes out of the way
histone acetyltransferase (HAT)
adds acetyl group to histone tails
histone deacetyltransferase (HDAT)
removes acetyl groups from histones
–> decreased transcription
beta-inferon
encodes antiviral protein inferno
is activated at high levels with viral infection
enhanceosome
moves nucleosomes out of the way for access to TATA box
GCN5
coactivator protein that acetylates nucleosome
CBP protein
coactivator with histone acetylase activity
recruits RNA polymerase II
epigenetics
study of inherited changes in gene expression without a change in the underlying DNA sequence
epigenetics is…
the inheritance of HOW the gene is expressed not WHAT genes are expressed
silencing is generated in DNA methylation without…
any change in the DNA sequence
what happens to one of the X chromosomes in females?
inactivated through methylation so double the genes aren’t expressed
