Molecular Bio (Exam 2): Operon

What is a regulatory protein that binds to DNA and inhibits transcription?

repressor.

What is a regulatory protein that binds to DNA and increases the rate of transcription?

activator.

Transcription regulation by a repressor is _________ control.

negative.

Regulation by an activator is considered to be _________ control.

positive.

What repressor protein prevents RNA polymerase from initiating transcription?

negative control.

What is a small effector molecule that causes the rate of transcription to increase?

inducer.

Genes that are regulated by inducers are _________ genes.

inducible genes.

What causes rate of transcription to increase by 1. binding to repressor protein to prevent it from binding to DNA or 2. bind to an activator protin and cause it to bind to DNA?

inducer.

What activator mechanism is required for RNA polymerase to initiate transcription (ex. catabolite activator protein).

positive control.

What is a small effector molecule that binds to a repressor protein, thereby causing the protein to bind to the DNA?

corepressor.

What binds to an activator protein and prevents it from binding to the DNA?

Corepressor.

The genes that are regulated by both corepressors and inhibitors to reduce the rate of transcription are _________ genes.

repressible.

What transcription control protein transcribes an enzyme-coding gene in response to appearance of its substrate?

Induction.

What transcription control suppresses transcription by the product of its enzyme pathway?

repression.

Induction and repression are regulated by what?

small molecules.

What small molecule is a substrate for induction?

inducer.

What small molecule is a substrate for repression?

corepressor.

What operon is an example of inducible regulation?

lac operon.

In inducible regulation, a gene is regulated by a __________ of its own enzyme pathway.

subsrate.

What operon is an example of repressible regulation?

trp operon.

In repressible regulation, a gene is regulated by a __________ of its enzyme pathway.

product.

Both induction and repression can be under __________ and __________ control.

positive; negative.

Negative control involves what protein?

repressor.

Positive control involves what protein?

activator.

Induction (transcription activation) involves what protein?

inducer.

Repression (transcription suppression) involves what protein?

corepressor.

Inducers inactivate __________ or activate __________.

repressor; activator.

Corepressors inactivate __________ or activate __________.

activator; repressor.

Trans-acting factors bind to __________-acting elements.

cis.

Lac operon contains three structural genes in the same location as the __________ gene.

regulatory.

Transcription expresses laxZYA as a single polycistronic __________.

mRNA.

LacZYA genes are highly expressed only when __________ is available, and __________ is not.

lactose; glucose.

Which gene encodes B-galactosidase, which breaks the lactose down into its two component sugars?

lacZ.

Which gene encodes lactose permease, which transports the lactose into the cells?

lacY.

The __________ gene, coding for lac repressor, is always expressed at low levels.

lacl.

lac repressor binds to lac operator and thereby __________ RNA polymerase function.

inhibits.

What does lac repressor bind to inhibit RNA polymerase function?

lac operator.

lac repressor is a tetramer made of two __________.

dimers.

The repressor consists of a __________-binding domain, __________-binding domain, and olligomerization domain.

DNA; inducer.

The DNA-binding domain in lac repressor binds to what?

major groove.

lac repressor is controlled by a small-molecular __________.

inducer.

Inducer binding causes a conformational change in DNA-binding domain, which prevents repressor from binding __________.

operator.

What control is defined by binding of a molecule to one site of a protein results in a conformational change of another site of the protein, thereby affecting its function.

allosteric control.

lac repressor binding to the operator is regulated by what kind of change in conformation?

allosteric.

Repressor protein binds to the double-stranded DNA sequence of the __________.

operator.

The operator is a __________ sequence.

palindromic.

Each inverted repeat of the operator binds to the DNA-binding domain (DBD) of one __________ subunit.

repressor.

Each inverted repeat of the operator binds to the __________ of one repressor subunit.

DBD (DNA-binding domain).

One DNA-binding domain binds to each __________ of the operator inverted repeat.

half.

Inducer-binding changes __________ conformation.

DBD (DNA-binding domain).

lac repressor binds to the three operators and interacts with RNA __________.

polymerase.

Each dimer in a repressor tetramer can bind an __________.

operator.

How many operators are in the lac operon?

3.

The repressor tetramer binds two operators simultaneously, which __________ repression by 50 fold.

increases.

Deletion of ___ or ___ operators decreases repression by 2-4 fold.

O2 or O3.

Binding of repressor at the lac operator stimulates binding of RNA polymerase at the __________.

promoter.

Binding of the repressor at the operator inhibits transcription __________.

initiation.

Mechanism of repressor function is __________ in each system

different.

The lac operon with the strongest binding is?

O1.

__-acting constitutive mutations identify the operator.

cis.

Mutations in the regulatory circuit may either abolish expression or cause __________ expression of the operon.

constitutive.

Uninducible mutations in the regulatory circuit may __________ expression.

abolish.

A mutation in operator that abolishes repressor-binding is a __________ mutation.

constitutive.

Removal of lacl (lacl^-) mutations cause __________ expression of lac operon.

constitutive.

When wild-type lacl was introduced to lacl^- cells, lac operon was regulated __________.

normally.

Mutations in DNA-binding domain (lacl^-d) are __________.

dominant.

lacl^s allele codes for repressor that cannot bind __________.

inducer.

The lac operon is not induced even if __________ is present when __________ is available.

lactose; glucose.

lac operon induction generates __________ and __________.

galactose; glucose.

An accumulation of glucose inhibits __________ of lac operon.

transcription.

The accumulation of glucose inhibiting transcription of lac operon is __________ repression.

catabolite.

Catabolite repressor protein (CAP) is required for __________ of genes with poor -35 and/or -10 box.

transcription.

What is required for transcription of genes with poor -35 and/or -10 box?

CAP.

CAP is activated by what?

cAMP.

cAMP levels are reduced by what?

glucose.

High glucose results in (active/inactive) CAP?

inactive.

The lac operon is not indued even if lactose is present when what is available?

glucose.

Accumulation of ________ inhibits transcription of lac operon.

glucose.

Catabolite repression refers to the accumulation of glucose inhibiting what?

transcription of lac operon.

CAP functions as a dimer, which binds to pentameric ________ repeat.

inverted.

CAP-binding site is right _______ of promoter.

upstream.

CAP activates the lac genes by binding what?

RNA polymerase.

CAP has what 2 domains?

DBD and activation domain.

The CAP activation domain interacts with the _______ of the alpha subunit of RNA polymerase and stabilizes the complex.

CTD (carboxyl-terminal domain).

The CAP activation domain interacts with the carboxyl-terminal domain of the ___ subunit of RNA polymerase and stabilizes the complex.

alpha.

CAP mediates the effect of _______, whereas Lac repressor mediates the ______ signal.

glucose; lactose.

The combined effect of lac and CAP regulators ensures that the lac genes are expressed at significant levels only when ______ is present but _______ is not.

lactose; glucose.

When glucose and lactose is present, there is a _______ level of lac transcription.

basal.

When glucose is present and lactose is not, lac transcription is _______.

leaky (almost none).

When lactose is present and glucose is not, there is a _______ level of lac transcription.

high.

The trp operon is negatively repressible by the level of its product, _________.

tryptophan.

Tryptophan activates an inactive _______, encoded by trpR.

repressor.

trp repressor acts on all loci that have a copy of its target _________ sequence.

operator.

aroH, trp operon, and trpR are all examples of what?

trp repressor target operator sequences.

trp repressor structure is?

tetramer.

Tryptophan is a what?

corepressor.

Attenuation regulates bacterial operons by controlling transcription termination at a site located before the first structural ________.

gene.

What is a terminator at which attenuation occurs?

attenuator.

trp operon attenuation is controlled by the rate of translation of the attenuator ____.

ORF.

trp operon attenuation depends on RNA ________ structure, which is regulated by movement of ribosome.

secondary.