bio 305 exam 4 Questions with 100% Verified Answers
Latest Update
Question: the basics of prokaryotic transcriptional regulation
Answer:
- genetic switches: the control of gene expression is governed by DNA-binding proteins that
recognize specific sequences of genes
- where transcription begins: the DNA segment that participates in this interaction is called
the promoter and the protein is the RNA polymerase
- whether transcription begins: promoter driven transcription takes place, activator and
repressor regulatory proteins
Question: tryptophan operon
Answer:
- set of 5 genes (A-E) that are regulated together
- gene order corresponds to reaction order in the biosynthetic pathway to build tryptophan
- governed by the level of trp in 2 ways: trp repressor and attenuation
- trp repressor: trans
- trpO: operator -> cis
- trp: corepressor
Question: trp repressor
Answer:
- a protein that binds to the operator site of the trp operon and inhibits transcription
- low tryptophan -> high expression of operon (and repressor inactive_
- high tryptophan -> operon repressed and repressor active
Question: attenuation
Answer:
- decreases the levels of the trpO expression when trp is plentiful
- controls the alternative folding of the mRNA synthesized from the 162-bp trp L (leader)
region
Question: trp leader (L) region
Answer:
at the 5' end of the trp operon mRNA before the first codon of the trpE gene
Question: how does attenuation work
Answer:
- it's post transcriptional
,- each mRNA transcribed from the trpL operon forms either a 2-3 stem loop or a 3-4 stem
loop
- the coupling of transcription and translation and the rate of translation determines the
type of stem loop that forms
Question: antitermination loop
Answer:
- 2-3 stem loop
- occurs when there is tryptophan starvation
- promotes transcription
Question: termination loop
Answer:
- 3-4 stem loop
- occurs when tryptophan is in abundance
- blocks transcription
Question: repressor/attenuator process of amino acids
Answer:
one signature of amino acid biosynthesis operons is the presence of multiple codons for the
amino acid being synthesized in a separate peptide encoded by the 5' leader sequence
Question: Riboswitches
Answer:
- a segment of mRNA that binds a small regulatory molecule to control gene expression by
modulating transcription or translation in bacteria
- exploits ability of RNA to fold and mimic termination loops for transcription
- sequesters/hides away other sequences that are important for translation
Question: alternative sigma factors of RNA polymerase
Answer:
- control of large numbers of genes in bacteria
- called regulons
- ex: when heat rises, sigma32 activates -> chaperones are expressed -> proteins refold
- activation of one sigma factor by another allows for robust integration of diverse
environmental signals
Question: rules of prokaryotic gene expression
Answer:
1. We can envision DNA as occupied by regulatory proteins binding to the operator sites
that they control.
, 2. The exact pattern of binding will depend on which genes are turned on or off and whether
activators or repressors regulate particular operons (transcriptional).
3. Catabolites can regulate activators and repressors allosterically
4. Alternative sigma factors can turn on genes in different locations (regulons) to face
unique conditions
5. A second level of regulation in amino acid biosynthesis operons is attenuation of
transcription mediated by the abundance of the amino acid and translation of a leader
peptide (co-transcriptional).
6. Riboswitches also control transcription and translation in a conceptually similar way as
#5
Question: cell fates
Answer:
determined and maintained by transcriptional and epigenetic mechanism
Question: six mechanisms of eukaryotic gene regulation
Answer:
- transcription initiation
- RNA processing
- RNA transport from nucleus to cytoplasm
- RNA stability
- translation efficiency
- protein activation/modification
Question: promoters in eukaryotes
Answer:
- TATA box: binding site for the TATA binding protein (TBP), one of the components of the
basal transcription factor
- after RNA polII recruitment, transcription can initiate 30 bp downstream from the TATA box
- cis-acting element
Question: promoter-proximal elements
Answer:
- In eukaryotes, regulatory sequences in DNA that are close to a promoter and that can bind
regulatory transcription factors.
- GC rich, CAAT, TATA
- cis-acting element
Question: enhancers
Answer:
- distance independent elements: can be found a considerable distance away from the gene
the regulate
Latest Update
Question: the basics of prokaryotic transcriptional regulation
Answer:
- genetic switches: the control of gene expression is governed by DNA-binding proteins that
recognize specific sequences of genes
- where transcription begins: the DNA segment that participates in this interaction is called
the promoter and the protein is the RNA polymerase
- whether transcription begins: promoter driven transcription takes place, activator and
repressor regulatory proteins
Question: tryptophan operon
Answer:
- set of 5 genes (A-E) that are regulated together
- gene order corresponds to reaction order in the biosynthetic pathway to build tryptophan
- governed by the level of trp in 2 ways: trp repressor and attenuation
- trp repressor: trans
- trpO: operator -> cis
- trp: corepressor
Question: trp repressor
Answer:
- a protein that binds to the operator site of the trp operon and inhibits transcription
- low tryptophan -> high expression of operon (and repressor inactive_
- high tryptophan -> operon repressed and repressor active
Question: attenuation
Answer:
- decreases the levels of the trpO expression when trp is plentiful
- controls the alternative folding of the mRNA synthesized from the 162-bp trp L (leader)
region
Question: trp leader (L) region
Answer:
at the 5' end of the trp operon mRNA before the first codon of the trpE gene
Question: how does attenuation work
Answer:
- it's post transcriptional
,- each mRNA transcribed from the trpL operon forms either a 2-3 stem loop or a 3-4 stem
loop
- the coupling of transcription and translation and the rate of translation determines the
type of stem loop that forms
Question: antitermination loop
Answer:
- 2-3 stem loop
- occurs when there is tryptophan starvation
- promotes transcription
Question: termination loop
Answer:
- 3-4 stem loop
- occurs when tryptophan is in abundance
- blocks transcription
Question: repressor/attenuator process of amino acids
Answer:
one signature of amino acid biosynthesis operons is the presence of multiple codons for the
amino acid being synthesized in a separate peptide encoded by the 5' leader sequence
Question: Riboswitches
Answer:
- a segment of mRNA that binds a small regulatory molecule to control gene expression by
modulating transcription or translation in bacteria
- exploits ability of RNA to fold and mimic termination loops for transcription
- sequesters/hides away other sequences that are important for translation
Question: alternative sigma factors of RNA polymerase
Answer:
- control of large numbers of genes in bacteria
- called regulons
- ex: when heat rises, sigma32 activates -> chaperones are expressed -> proteins refold
- activation of one sigma factor by another allows for robust integration of diverse
environmental signals
Question: rules of prokaryotic gene expression
Answer:
1. We can envision DNA as occupied by regulatory proteins binding to the operator sites
that they control.
, 2. The exact pattern of binding will depend on which genes are turned on or off and whether
activators or repressors regulate particular operons (transcriptional).
3. Catabolites can regulate activators and repressors allosterically
4. Alternative sigma factors can turn on genes in different locations (regulons) to face
unique conditions
5. A second level of regulation in amino acid biosynthesis operons is attenuation of
transcription mediated by the abundance of the amino acid and translation of a leader
peptide (co-transcriptional).
6. Riboswitches also control transcription and translation in a conceptually similar way as
#5
Question: cell fates
Answer:
determined and maintained by transcriptional and epigenetic mechanism
Question: six mechanisms of eukaryotic gene regulation
Answer:
- transcription initiation
- RNA processing
- RNA transport from nucleus to cytoplasm
- RNA stability
- translation efficiency
- protein activation/modification
Question: promoters in eukaryotes
Answer:
- TATA box: binding site for the TATA binding protein (TBP), one of the components of the
basal transcription factor
- after RNA polII recruitment, transcription can initiate 30 bp downstream from the TATA box
- cis-acting element
Question: promoter-proximal elements
Answer:
- In eukaryotes, regulatory sequences in DNA that are close to a promoter and that can bind
regulatory transcription factors.
- GC rich, CAAT, TATA
- cis-acting element
Question: enhancers
Answer:
- distance independent elements: can be found a considerable distance away from the gene
the regulate
