Exam 3 Genetics - Gene Regulation

The trp operon is regulated by a repressor protein and by ________ in which transcription is stopped prematurely.

attenuation

The Lac repressor protein binds to the operator and

blocks transcription

During attenuation, transcription begins,

but it is terminated before the entire mRNA is made.

Inducible operons usually encode ______ enzymes, and repressible operons usually encode ______ enzymes.

catabolic; anabolic

n the thi operon in B. subtilis, when levels of TPP are high, the mRNA folds into a stem-loop structure that

causes attenuation.

The ______ gene encodes a repressor protein.

lacI

A translational repressor protein binds to

mRNA near the start codon.

When TPP levels are low, the mRNA of the E. coli thiMD operon forms a stem-loop structure that Multiple choice question.

makes the Shine-Dalgarno sequence available to the ribosome.

A strain of bacteria containing F' factor genes is called a ____ or a partial diploid.

merozygote

When lactose is depleted from the environment,

the intracellular concentration of allolactose falls.

In bacteria, the most common way to regulate gene expression is by influencing

the rate of transcription initiation.

Monod, Jacob, and Pardee learned about the lac operon using bacterial strains called merozygotes. Since lacI encodes a diffusible protein, in a merozygote, the gene on the _________ could supply the mutant cell with functional repressor protein.

F' factor

What is the name for a strain of bacteria containing an F' factor?

Merozygote

What type of regulation does not need to be adjacent to the gene(s) it is regulating?

Trans-acting factor

In which type of regulation do riboswitches control access to the Shine-Dalgarno sequence?

Translation

Enzyme adaptation refers to the observation that

a particular enzyme appears within a cell only after the cell has been exposed to the substrate for that enzyme.

The observation that a particular enzyme appears within a cell only after a cell has been exposed to the enzyme's substrate is called enzyme _________

adaptation

A conformational change that prevents the repressor from binding to the lac operator occurs when ___________ binds to the lac repressor.

allolactose

The binding of ______ to the lac repressor promotes a conformational change that prevents the repressor from binding to the lac operator.

allolactose

The intracellular concentration of the inducer______ remains high as long as lactose is available in the environment.

allolactose

The small effector molecule ________ prevents the lac repressor from binding to the operator site

allolactose

In the E. coli thiMD operon, the 5' end of the mRNA folds into a structure with a stem-loop called the Shine-Dalgarno , ________ that keeps the Shine-Dalgarno sequence accessible to the ribosome.

antisequestor

In the thi operon in B. subtilis, when levels of TPP are low, the 5' end of the mRNA forms a stem-loop structure called a(n) ________ that allows transcription to continue.

antiterminator

A DNA segment that must be adjacent to the gene(s) it regulates is a ______ - _________ element

cis-acting

The probability that allolactose will bind to the lac repressor depends on the allolactose ________ in the bacterial cell.

concentration/amount

Unregulated genes have ______

constant levels of expression.

Posttranslational regulation refers to

control of proteins already in the cell

The binding of the lac repressor to the operator shuts down transcription from the lac operon when lactose is

depleted from the environment.

The normal lacI gene on the F' factor could rescue the lacI-mutants because the product of the lacI gene encodes a _____

diffusible protein.

The genes in the trp operon encode

enzymes used in tryptophan biosynthesis.

True or false: Gene regulation is constant.

false

True or false: The rate of transcription initiation rarely influences overall gene expression

false

When the product of a gene produced in a metabolic pathway inhibits an enzyme that acts early on in the pathway it is called

feedback inhibition

In catabolite repression, transcription is influenced by the presence of

glucose

In feedback inhibition, the final product in a metabolic pathway

inhibits an enzyme that acts early in the pathway.

In attenuation, transcription

is stopped prematurely.

It has been shown that the lac operon has three _______ sites to which the lac repressor can bind.

operator

A(n) ______ is a group of two or more genes under the transcriptional control of a single promoter.

operon

An operon encodes a _________ mRNA, an RNA that contains the sequences of two or more genes.

polycistronic

The term _________ regulation refers to control of proteins already present in the cell.

posttranslational

Allolactose is a small effector molecule that binds to the lac repressor and

prevents the repressor from binding to DNA

Anabolic enzymes are usually encoded by ______ operons, and ______ operons usually encode catabolic enzymes

repressible; inducible

An operon is a group of two or more genes under the transcriptional control of _______

single promoter

A translational repressor protein may bind to the mRNA and

stabilize a secondary structure that prevents translation.

Studies indicate that the lac operon has ______ operator site(s) for the lac repressor.

three

the genes in the trp operon :

trp A trp B trp C trp D trp E