Exam 2 Genetics

Interactions of catabolite activator protein and lac repressor in regulating transcription of the lac operon:

-CAP site bind site for CAP. -cAMP to bind to CAP site-increase transcription. -Increase glucose and decrease cAMP. -Operator site is binding site for lac repressor. -Allolactose prevent lac repressor from binding to DNA-> increase transcription.

Difference between inducible and repressible regulation

-Inducible genes require inducer to increase transcription. -Repressible regulation require repressor to decrease transcription.

Role of the repressor in the lac operon:

-Lac repressor protein binds to sequence of nucleotides found within lac operator site. -Ability of lac repressor to bind the operator site depends on whether or not allolactose (Inducer) is bound to it.

How the " small effector molecules" affect transcription: inducers and their effect on activators and repressors; corepressors and inhibitors and their effect on activators and repressors.

-Small effector molecules play critical role in transcriptional regulator. Effector molecules DO NOT bind directly to DNA to alter transcription. -An effector molecule exerts its effects by binding to a repressor or activator. -The binding of the effector molecule causes a conformational change in the regulatory protein and thereby influences whether the protein can bind to DNA. -Genetic regulatory proteins that respond to small effector molecules typically have two binding sites: One site where the protein binds to the DNA; the other is the binding site for the effector molecule. -Inducer: A small effector molecule that binds to a genetic regulatory protein and thereby increases the rate of transcription. An inducer may accomplish this in two ways: It could bind to a repressor protein and prevent it from binding to the DNA. It could bind to an activator protein and cause it to bind to DNA.

During attenuation, when tryptophan levels are high, the_____________ stem-loop forms and transcription ________________ the trpL gene.

3-4 / ends just past.

An example of a post translational covalent modification that may regulate protein function is..

All of the above ( Phosphorylation, acetylation, methylation.)

The sequential use of two sugars by a bacterium is known to be __________.

Diauxic

On its chromosome, an E.Coli cell has a genotype of lac-, lacZ+, lacY+, and lacA+. It has an F' factor with a genotype of lacl+, lacZ+, lacY+, and lacA+. What is the expected level of expression of the lac operon genes in the absence of lactose?

Neither lac operon will be expressed.

_____________ mRNA contains the coding sequence for two or more structural genes.

Polycistronic

Operons involved with the biosynthesis of molecules such as amino acids are most likely to be regulated in which of the following ways?

The product of the biosynthetic pathway represses transcription.

What is an operon?

a group of genes under the control of a single promoter.

Which of the following combinations will cause transcription to be activated?

a repressor plus an inducer.

The binding of ____________ to lac repressor causes lac repressor to ________ to the operator site, thereby _____________ transcription.

allolactose /not bind/ increasing.

The action of a small effector molecule, such as allolactose is called___________.

allosteric regulation

_____________ an RNA strand that is complementary to a strand of mRNA.

antisense RNA

When tryptophan binds to trp repressor, this causes trp repressor to ____________ to the trp operator and _________________ transcription.

bind / inhibit.

Translation can be regulated by

both translational repressors and antisense RNA.

How does exposing an E.Coli cell to glucose affect regulation of lac operon via CAP?

cAMP does not bind to CAP and transcription is decreased.

The lac operon is transcriptionally regulated in a second way, known as ______________.

catabolite repression

unregulated genes are also called..

constitutive genes

A second strategy to control the function of proteins is the __________________ of their structure.

covalent modification

________________ is produced from ATP via an enzyme known as adenylyl cyclase.

cyclic-AMP (cAMP)

Francois Jacob and Jacques Monod research into genes and gene regulation stemmed from an interest in phenomenon is known as.....

enzyme adaptation

A common mechanism for regulating the activity of a metabolic enzyme is _________________.

feedback inhibition

For a riboswitch that controls transcription, the binding of a small molecule such as TPP controls whether the RNA

has an anti terminator or terminator stem-loop.

An____________ binds to an activator protein and prevent it from binding to DNA.

inhibitor

What is a sequence of bases that provides a binding site for a repressor protein called lac repressor?

operator site

a group of two or more genes that are transcribed from single promoter is...

operon

The term _____________ means " after translation is completed".

post translational

To facilitate transcription, an operon is flanked by a _______________ that signals the beginning of transcription.

promoter

A repressor is a _____________ that ___________________ transcription.

regulatory protein / inhibits.

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

repressor

In 2001 and 2002, researchers in a few different laboratories discovered a mechanism of gene regulation called a ______________.

riboswitch

How antisense RNA can stop expression of a protein as in the ompF gene.

-Translational regulatory protein. -Antisense RNA (translational repressor): RNA strand that is complementary to strand of mRNA. RNA bind to mRNA to form double-stranded structure which mRNA cannot be translated to protein.

Role of the repressor in trp operon

-Tryptophan as compressor. -Trp repressor needs tryptophan to bind to operatory site. -During attenuation, transcription actually begins but it is terminated before entire mRNA is made. -When attenuation occurs, mRNA from operon is made as short piece that terminates shortly past the trpL gene. Will not encode proteins required for tryptophan biosynthesis.

General trends regarding inducible regulation and catabolic genes, repressible regulation and anabolic genes.

-When genes operon encode proteins which function in catabolism they are usually regulated in an inducible manner. -The substance to be broken down or related compound often acts as reducer. Genes that encode these anabolic enzymes tend to be regulated by repressible mechanism. -Corepressor or inhibitor is commonly small molecule that is product of the enzymes biosynthetic activities.

The _________ is a DNA sequence recognized by an activator protein called__________.

CAP site/ CAP

What is the difference between constitutive vs. regulated genes?

Constitutive genes are always being expressed (at basal/regular level) but regulated genes are only expressed under certain necessary conditions in order to save cellular energy.

A ______________ is a small molecule that binds to repressor protein, thereby causing the protein to bind to the DNA.

corepressor

a regulatory protein that increases rate of transcription is..

activator