Bio 261 Exam 2 (Powell) Study Guide
with Actual Answers 2025-2026
Updated.
Activator protein - Answer a protein that activates the expression of the gene by stimulating
the RNA polymerase to bind to the promoter region. Hence, it brings about positive control of
the gene; stimulates transcription
recognize - Answer Activator protein helps RNA polymerase ______ promoter.
-may bend DNA structure
-may interact directly with RNA polymerase
Allosteric protein - Answer - a protein containing an active site for binding substrate and an
allosteric site for binding an effector molecule such as the end product of a biochemical
pathway
attentuation - Answer a mechanism for controlling gene expression that terminates
transcription after initiation but before a full-length messenger RNA is produced
Autoinducer - Answer - a small signal molecule that takes part in quorum sensing
-diffuses freely across the cell envelope
-reaches high concentrations inside cell only if many cells are nearby and making the same
-binds to specific activator protein or sensor kinase, triggering transcription of specific genes
Aliivibrio fischeri - Answer Quorum sensing first discovered as mechanism regulating light
production in bacteria including ______
Global control systems - Answer ________: regulate expression of many different genes
simultaneously (e.g., lactose operon and maltose regulon)
Catabolite repression - Answer the suppression of alternative catabolic pathways by a
preferred source of carbon and energy
-controls use of carbon sources if more than one is present
-synthesis of unrelated catabolic enzymes (e.g., lactose operon & maltose regulon) is repressed
if glucose is present in growth medium
-is an example of global control
,Cyclic AMP - Answer - a regulatory nucleotide that participates in catabolite repression
Feedback inhibition - Answer - a process in which an excess of the end product of a
multistep pathway inhibits activity of the first enzyme in the pathway
Gene expression - Answer - transcription of a gene followed by translation of the resulting
mRNA into protein
Heat shock proteins - Answer proteins induced by high temperature (or certain other
stresses) that protect against high temperature, especially by refolding partially denatured
proteins or by degrading them
Induction - Answer production of an enzyme in response to a signal (often the presence of
the substrate for the enzyme)
Negative control - Answer a mechanism for regulating gene expression in which a repressor
protein prevents transcription of genes
Operon - Answer cluster of consecutive genes whose expression is under control of a single
operator; two or more genes transcribed into a single RNA and under the control of a single
regulatory site
Positive control - Answer a mechanism for regulating gene expression in which an activator
protein functions to promote transcription of genes
Quorum sensing - Answer a regulatory system that monitors the population level and
controls gene expression based on cell density
Repression - Answer prevention of the synthesis of an enzyme in response to a signal
Repressor protein - Answer blocks transcription; a protein which inhibits the activity of the
gene by binding to the operator region, upstream of the transcription start site. Since the
operator is downstream of the promoter, the RNA polymerase cannot bind to the promoter &
initiate transcription- brings about negative control of the gene
Response regulator protein (part of two component regulatory system) - Answer in
cytoplasm, a protein that is phosphorylated by a sensor kinase and then acts as a regulator,
often by binding to DNA; DNA-binding protein that regulates transcription
, Sensor kinase protein (part of two component regulatory system) - Answer in cytoplasmic
membrane, a protein that detects environmental signal and autophosphorylates itself in
response
Stringent response - Answer a regulatory mechanism used to survive that detects nutrient or
environmental stresses and antibiotics
-shuts down macromolecule synthesis and activates stress survival pathways
Two-component regulatory system - Answer a regulatory system consisting of two proteins:
a sensor kinase and a response regulator
synthesis - Answer Enzyme repression is widespread in bacteria as a means of controlling the
______ of enzymes required for the production of amino acids and the nucleotide precursors
purines and pyrimidines.
waste energy and nutrients - Answer Enzyme repression is a way of ensuring that the
organism does not: _______________________ synthesizing unneeded enzymes.
enzyme repression - Answer -when a certain molecule __, prevent the manufacture of an
enzyme
-molecule will often combine w/ another molecule and the duo is able to block the operation of
the operator by outcompeting w/ the polymerase for the binding site on the operator
-or they can bind directly to the polymerase & prevent its further binding to the operator region
-typically operates by feedback inhibition
-either way, result: blockage of the transcription of a particular gene
biosynthetic (anabolic) - Answer Enzyme repression typically affects _________________
enzymes.
degradative (catabolic) - Answer Enzyme induction usually affects ______________
enzymes.
effectors - Answer -collective term for inducers and repressors
-indirectly affect transcription by binding to specific DNA-binding proteins
-typically small molecules
-can be structural analogs of substrates/products
enzyme induction - Answer -a process where an enzyme is manufactured in response to the
presence of a specific molecule: typically a compound that the enzyme acts upon
with Actual Answers 2025-2026
Updated.
Activator protein - Answer a protein that activates the expression of the gene by stimulating
the RNA polymerase to bind to the promoter region. Hence, it brings about positive control of
the gene; stimulates transcription
recognize - Answer Activator protein helps RNA polymerase ______ promoter.
-may bend DNA structure
-may interact directly with RNA polymerase
Allosteric protein - Answer - a protein containing an active site for binding substrate and an
allosteric site for binding an effector molecule such as the end product of a biochemical
pathway
attentuation - Answer a mechanism for controlling gene expression that terminates
transcription after initiation but before a full-length messenger RNA is produced
Autoinducer - Answer - a small signal molecule that takes part in quorum sensing
-diffuses freely across the cell envelope
-reaches high concentrations inside cell only if many cells are nearby and making the same
-binds to specific activator protein or sensor kinase, triggering transcription of specific genes
Aliivibrio fischeri - Answer Quorum sensing first discovered as mechanism regulating light
production in bacteria including ______
Global control systems - Answer ________: regulate expression of many different genes
simultaneously (e.g., lactose operon and maltose regulon)
Catabolite repression - Answer the suppression of alternative catabolic pathways by a
preferred source of carbon and energy
-controls use of carbon sources if more than one is present
-synthesis of unrelated catabolic enzymes (e.g., lactose operon & maltose regulon) is repressed
if glucose is present in growth medium
-is an example of global control
,Cyclic AMP - Answer - a regulatory nucleotide that participates in catabolite repression
Feedback inhibition - Answer - a process in which an excess of the end product of a
multistep pathway inhibits activity of the first enzyme in the pathway
Gene expression - Answer - transcription of a gene followed by translation of the resulting
mRNA into protein
Heat shock proteins - Answer proteins induced by high temperature (or certain other
stresses) that protect against high temperature, especially by refolding partially denatured
proteins or by degrading them
Induction - Answer production of an enzyme in response to a signal (often the presence of
the substrate for the enzyme)
Negative control - Answer a mechanism for regulating gene expression in which a repressor
protein prevents transcription of genes
Operon - Answer cluster of consecutive genes whose expression is under control of a single
operator; two or more genes transcribed into a single RNA and under the control of a single
regulatory site
Positive control - Answer a mechanism for regulating gene expression in which an activator
protein functions to promote transcription of genes
Quorum sensing - Answer a regulatory system that monitors the population level and
controls gene expression based on cell density
Repression - Answer prevention of the synthesis of an enzyme in response to a signal
Repressor protein - Answer blocks transcription; a protein which inhibits the activity of the
gene by binding to the operator region, upstream of the transcription start site. Since the
operator is downstream of the promoter, the RNA polymerase cannot bind to the promoter &
initiate transcription- brings about negative control of the gene
Response regulator protein (part of two component regulatory system) - Answer in
cytoplasm, a protein that is phosphorylated by a sensor kinase and then acts as a regulator,
often by binding to DNA; DNA-binding protein that regulates transcription
, Sensor kinase protein (part of two component regulatory system) - Answer in cytoplasmic
membrane, a protein that detects environmental signal and autophosphorylates itself in
response
Stringent response - Answer a regulatory mechanism used to survive that detects nutrient or
environmental stresses and antibiotics
-shuts down macromolecule synthesis and activates stress survival pathways
Two-component regulatory system - Answer a regulatory system consisting of two proteins:
a sensor kinase and a response regulator
synthesis - Answer Enzyme repression is widespread in bacteria as a means of controlling the
______ of enzymes required for the production of amino acids and the nucleotide precursors
purines and pyrimidines.
waste energy and nutrients - Answer Enzyme repression is a way of ensuring that the
organism does not: _______________________ synthesizing unneeded enzymes.
enzyme repression - Answer -when a certain molecule __, prevent the manufacture of an
enzyme
-molecule will often combine w/ another molecule and the duo is able to block the operation of
the operator by outcompeting w/ the polymerase for the binding site on the operator
-or they can bind directly to the polymerase & prevent its further binding to the operator region
-typically operates by feedback inhibition
-either way, result: blockage of the transcription of a particular gene
biosynthetic (anabolic) - Answer Enzyme repression typically affects _________________
enzymes.
degradative (catabolic) - Answer Enzyme induction usually affects ______________
enzymes.
effectors - Answer -collective term for inducers and repressors
-indirectly affect transcription by binding to specific DNA-binding proteins
-typically small molecules
-can be structural analogs of substrates/products
enzyme induction - Answer -a process where an enzyme is manufactured in response to the
presence of a specific molecule: typically a compound that the enzyme acts upon
