Chapter 16: Gene Regulation in Bacteria

_________ RNA is a piece of RNA that is complementary to the mRNA.

Antisense

___________ are effector molecules that bind to repressors, causing the repressor to bind to the DNA. They decrease the rate of ___________.

Corepressors , transcription.

___________ molecules do not interact directly with the DNA, but rather directly with the __________ or ___________ . This usually results in a ____________ change in the activator or repressor.

Effector , repressors or activators , conformational

__________ means that an enzyme appears in the cell only after the cell has been exposed to the substrate for that enzyme.

Enzyme adaptation

_____________ means that the level of gene expression can vary under different conditions.

Gene regulation

_________have a promoter at the beginning and a terminator at the end. In addition, there is an operator site that controls the ability of ___________ the to transcribe the operon.

Operons , RNA polymerase

___________ regulation refers to the functional control of proteins that are already present in the cell.

Posttranslational

The lac repressor protein binds to the operator and prevents the _________ from recognizing the promoter and transcribing the lacZ, lacY and lacA genes. This is an example of an ________, _________ control mechanism.

RNA polymerase , inducible, negative

__________ inhibit transcription, which is called ________ control. _________ increase transcription, which is called _________ control.

Repressors , negative , Activators , positive

Translational repressors may inhibit translation by binding to the ___________ sequence, or by binding to a region of the mRNA that promotes an RNA secondary structure that inhibits translation.

Shine-Dalgarno

lacY - encodes _____________.

a lactose permease, which actively transports lactose into the cell.

lacA - encodes ______________.

a transacetylase enzyme that modifies the lactose

cyclic-AMP (cAMP) molecule is produced from ATP by ____________ . cAMP binds to an activator protein called CAP (catabolite activator protein). This is an __________ system, under _______ control.

adenyl cyclase , inducible , positive

The lac repressor will only occur if ___________ is bound to it.

allolactose

Binding to a site on the enzymatic apart from the active site and inducing a conformational change in the enzyme is known as ____________ regulation.

allosteric

The majority of gene regulation in __________ is at the transcriptional level.

bacteria

A second mechanism of lac operon regulation is called __________repression. The presence of ___________ in the cell represses the lac operon.

catabolite , glucose

An allosteric enzyme has two different binding sites. The ________ is responsible for the binding of the substrate. The ___________ allows for a means of turning the enzyme off, usually by a conformational change to the enzyme and catalytic site.

catalytic site , regulatory site

Unregulated genes, that have constant levels of expression, are called ____________. The majority of genes are __________.

constitutive genes , regulated.

A common mechanism of regulation for metabolic enzymes is ________ inhibition. In this case the final product of the pathway inhibits the activity of one or more enzymes in the pathway.

feedback

Regulation may occur at any stage of ______________.

gene expression

If placed in an environment containing both glucose and lactose, E.coli will use the _________ first. This sequential use of sugars is called _______ growth.

glucose , diauxic

inducers are effector molecules that cause an increase in transcription. Genes that are regulated in this manner by inducers are called ___________.

inducible.

Some regulation occurs during ___________ , __________ , and _________.

initiation, elongation, and termination of translation.

Two regulatory sites are located near the _________ . The operator provides a location for repressor proteins to bind, and the CAP site is a DNA sequence recognized by an activator protein called _____________.

lac operon , catabolite activator protein (CAP).

The binding of cAMP to CAP causes the cAMP-CAP complex to bind to the CAP site near the ___________. This increases the rate of ___________.

lac promoter , transcription.

The lacI gene (not part of the operon) encodes a _________ , which is transcribed at low levels in the cell.

lac repressor

The ____________ has a measurable affinity for allolactose. The likelihood that allolactose will bind to the repressor is dependent on the ___________ of the allolactose.

lac repressor , concentration

The _________ gene acts as a binding site for a repressor protein.

lacI

The lac operon contains _______ , ______ , ________ , ______ , and _________ components.

lacP lacO lacZ lacY lacA

As the cell utilizes ____________ , the allolactose levels will fall, allowing the repressor to bind again to the operator.

lactose

lacO - the __________.

operator

the lacI gene does not need to be located near the _______ to influence activity, and thus is not the binding site for a repressor protein. Rather, it encodes a __________ that diffuses to the operon.

operon , repressor protein

Inhibitors bind to an activator protein and __________ it from binding to the DNA. Genes that are regulated in this manner are called __________.

prevent , repressible.

In bacteria, structural genes are often arranged together under the control of a single_________. This is called an ________ . Transcription of an operon creates a __________ , which contains instructions for two or more structural genes.

promoter , operon , polycistronic mRNA

lacP - the __________.

promoter.

Transcriptional regulation involves the actions of regulatory _____________ that bind to the ______ and affect the rate of transcription.

proteins , DNA

Enzymes may also be modified by covalent modification of their structure: a. This may include _______ processing, _________ formation, or the attachment of ___________ , ___________ or ___________ to the enzyme. b. This process is known as ______________ modification.

proteolytic , disulfide bond , sugars , functional groups or lipids , posttranslational covalent

The processes of metabolism, response to environmental stress, and cell division are all cell processes that require __________.

regulation.

The binding of allolactose produces a conformational change in the__________ , preventing it from binding to the _________ and allowing transcription.

repressor , operator

lacI gene encodes a ___________ , and is not part of the operon.

repressor protein

The translation of mRNA can be influenced by proteins that influence the ability of the _________ to form a polypeptide.

ribosome

During induction of the operon, the concentration of the allolactose _____________, making it more likely that the allolactose will bind to the repressor, causing it to release from the __________.

rises , operator.

The study of mutations in the lac operon has led to the identification of ________ operator sites in the lac operon . It is believed that the repressor must bind to two of the three of the _________ sites to repress transcription, One of these sites must be ______.

three , operator , O1 .

A____________ factor does not require the DNA (gene) producing the factor to be in close proximity to its site of action. ________ are able to work "in trans". A cis-effect occurs when the DNA segments (genes) must be physically connected. DNA sequences are __________ factors.

trans-acting , Proteins , cis-acting

Translational regulatory proteins recognize sequences within the mRNA . These are called ___________.

translational repressors.

lacZ - encodes ___________.

β-galactosidase, which enzymatically cleaves lactose.

Enzyme adaptation was studied extensively by Jacob and Monod ,They examined __________ metabolism in E. coli. Their experiments indicated that: a. Exposure to lactose causes a 1,000 to 10,000-fold _________ in lactose enzymes. b. This was due to an increase in the synthesis of the _________. c. The_________ of lactose abruptly terminated the synthesis of enzymes. d. Mutations indicated that a __________ encoded for each enzyme.

lactose , increase , enzymes , removal , separate gene

Effector molecules are named by how they affect ___________ when they are present in the cell. Regulatory proteins are named by how they___________ with the DNA.

transcription , interact