CH 16

Riboswitches can regulate

*splicing *translation *transcription *RNA stability

How do a corepressor and an inhibitor differ?

A corepressor binds to a repressor protein, while an inhibitor binds to an activator protein

Proteins binding Catabolite acitivator protein

CAP site

Which processes are regulated at the genetic level

Cell division Response to the environment Metabolism

Gene expression is always the same

False

Gene regulation is constant

False

- researched (with Monod) lactose metabolism in bacteria and established many of the principles of enzyme adaptation

Jacob, Franҫois

determined the crystal structure of lac repressor and confirmed that its structure allows it to bind two operator sites (1996).

Lewis, Mitchell

in the 1950s who studies the lac operon in E. coli.?

Monod, Jacob and Pardee

- researched (with Jacob) lactose metabolism in bacteria and established many of the principles of enzyme adaptation

Monod, Jacques -

Proteins binding Repressor

Operatorq

experimentally determined (with Monod and Jacob) that the lacI gene encodes a repressor protein that is not part of the lac operon.

Pardee, Arthur

If CAP could not bind to its CAP site, then what would be the result? Assume lactose is present in this scenario.

Transcription would be difficult to activate in the absence of glucose.

The transport of glucose into a bacterial cell causes the intracellular level of cyclic-AMP to fall because the enzyme ___ ___ is inhibited

adenylyl cyclase

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

allolactose

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

allolactose

An enzyme may contain two sites: a catalytic site, and a regulatory or ______ site

allosteric

A regulatory site on a protein where an effector molecule binds is called a

allosteric site

Mutations in the gene for the lac repressor that result in a lac repressor that cannot bind allolactose would mean that transcription from the lac operon is

always repressed

The trp operon is regulated by a repressor and by _____ in which transcription I stopped prematurely

attenuation

Transcription begins but terminates before the entire mRNA is made during

attenuation

Riboswitches may be found in

bacteria, archaea, fungi and plants

The Lac repressor proteins binds to the operator and

blocks transcription

When tryptophan levels are low, the trp repressor ___ bind to the operator site. RNA polymerase ___ transcribe the trp operon.

cannot; can

Induced operons usually encode _____ enzymes, and repressible operons usually encode _____ enzymes.

catabolic; anabolic

The somewhat imprecise term that describes how transcriptional regulation is influenced by glucose is ____ ____

catabolite repression

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

cis-acting

Antisense RNA is an RNA strand that is _____to an mRNA molecule

complementary

Unregulated genes are also called

constitutive genes

What type of genes encode proteins the bacteria cell needs all the time

constitutive genes

The product of an operon may act as a _____ if the operon is repressible

corepressor

Genes that are regulated by inducers are called repressible genes.

false

In catabolite repression, transcription is influenced by the presence of

glucose

The transport of ___ into a cell causes a ___ in the concentration of cyclic-AMP by inhibiting adenylate cyclase

glucose; decrease

In feedback inhibition, the final product in a metabolic pathway

inhibits an enzyme that acts early in the pathway

Genetic regulation of translation is usually aimed at preventing the _____ step

initiation

When translation is regulated genetically, which phase of translation is usually blocked?

initiation

The following are protein-encoding genes in the lac operon

lacA, lacY, lacZ

A stain of bacteria containing F (prime ) facto genes is called a ___, or a partial diploid

merozygote

The lac operon is under what type of control?

negative control

A loss-of-function mutation in a gene encoding a repressor has the same effect as a mutation in the

operator site

An ____ 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

Transcription regulation by an activator is consider to be ___ control

positive

The term_____ regulation refers to control of proteins already present in the cell

posttranslational

Types of _____ covalent modifications include disulfide bond formation and attachment of prosthetic groups

posttranslational

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

prevents the repressor from binding to DNA

Proteins binding RNA polymerase

promoter

A regulatory protein that binds to DNA and inhibits transcription is a

repressor

An inducer could bind to an _____ and prevent it from binding to the DNA, or it could bind to a ____ and cause it to bind to the DNA

repressor; activator

an RNA molecule that can exist in two different secondary conformation and thereby affect gene regulation is known as a

riboswitch

A translational repressor protein may bind to the mRNA and

stabilize a secondary structure that prevents translation

When lactose is depleted from the environment,

the intracellular concentration of allolactose falls

The corepressor for a repressible operon may be

the product of that operator

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

the rate of transcription elongation

The mRNA made form the trpL gene contains codons for 14 amino acids that form

the trp leader peptide

Riboswitches have been shown to have regulation of ______?

transcription and translation

Genes in the trp operon

trpL, trpE, trpD, trpC, trpB, trpA