Ch 15.1 and 15.2- Regulation of Gene Expression

corepressor

A lack of which of the following molecules would result in the cell's inability to "turn off" genes? A. operon B. inducer C. promoter D. corepressor

Allolactose binds to the repressor protein.

Allolactose, an isomer of lactose, is formed in small amounts from lactose. An E. coli cell is presented for the first time with the sugar lactose (containing allolactose) as a potential food source. Which of the following processes occurs when the lactose enters the cell? A. Allolactose binds to the repressor protein. B. The repressor protein and allolactose bind to RNA polymerase. C. Allolactose binds to the operator. D. The repressor protein attaches to the regulator. E. Allolactose binds to the inducer.

distal control elements or enhancers

Control elements located far from the genes they regulate are also called __________. A. general transcription factors B. specific transcription factors C. proximal control elements or enhancers D. distal control elements or enhancers E. activators

inactivate genes

DNA methylation is a mechanism used by eukaryotes to __________. A. facilitate the binding of DNA to intermediate filaments B. increase the rate of transcription C. inactivate genes D. terminate transcription E. cause apoptosis

inhibit the activity of the first enzyme in the pathway and repress the genes encoding all enzymes in the pathway

How does an abundance of tryptophan inhibit the production of more tryptophan? A. inhibit the activity of all three enzymes in the pathway and repress expression of the genes encoding all subunits of the enzymes in the pathway B. repress expression of the genes encoding all subunits of the enzymes in the pathway C. inhibit the activity of all three enzymes in the pathway D. inhibit the activity of the first and second enzymes in the pathway and repress expression of the genes encoding all subunits of the enzymes in the pathway E. inhibit the activity of the first enzyme in the pathway and repress the genes encoding all enzymes in the pathway

There are mRNAs that are being translated at the same time as they are being transcribed.

If you were to observe gene expression in a cell, which of the following clues would indicate that the cell is prokaryotic? A. There are mRNAs that are being translated at the same time as they are being transcribed. B. A single gene has many RNA polymerases bound to it. C. A single mRNA has many ribosomes bound to it. D. Spliceosomes are carrying out RNA splicing.

to help RNA polymerase transcribe certain genes

In humans, the steroid hormone testosterone enters cells and binds to specific proteins, which in turn bind to specific sites on the cells' DNA. The result is expression of genes associated wtih male sexual characteristics. What is the function of these proteins? A. to methylate the DNA so that its genes can be transcribed B. to help RNA polymerase transcribe certain genes C. to alter the pattern of DNA splicing D. to cause mutations in the DNA E. to promote recombination

It is deactivated whenever tryptophan is added to the growth medium.

The tryptophan operon in some bacteria is a repressible operon. Which of the following statements correctly describes this operon? A. It is deactivated whenever tryptophan is added to the growth medium. B. It is activated only when glucose is present in the growth medium. C. It is permanently active. D. It is activated only when tryptophan is present in the growth medium.

It makes it transcriptionally inactive.

What effect does methylation have on DNA? A. It allows it to be unwound in preparation for protein synthesis. B. It activates transcription. C. It allows it to be replicated nearly continuously. D. It makes it transcriptionally inactive.

initiation of translation

What process is shown in the diagram? A. elongation B. codon recognition C. peptide bond formation D. initiation of translation

alter the level of production of various enzymes

Which of the following activities can prokaryotes carry out in response to certain chemical signals? A. inactivate their mRNA molecules B. increase the number and responsiveness of their ribosomes C. alter the level of production of various enzymes D. turn off translation of their mRNA

RNA polymerase and the promoter

Which of the following are required for the process of transcription? A. RNA polymerase and the promoter B. DNA and DNA polymerase C. transcription factors and amino acids D. tRNA and RNA polymerase

repressor

Which of the following is a protein product of a regulatory gene? A. inducer B. operon C. repressor D. promoter

chromatin modification

Which of the following is not a post-transcriptional stage of gene regulation? A. degradation of mRNA B. protein processing and degradation C. chromatin modification D. RNA processing E. transport of mRNA from nucleus to cytoplasm

inducer

Which of the following molecules, when taken up by the cell, binds to the repressor so that the repressor no longer binds to the operator? A. promoter B. ubiquitin C. inducer D. repressor

RNA polymerase must bind to the promoter, and the repressor must be inactive.

Which of the following must occur in order for a repressible operon to be transcribed? A. RNA polymerase and the active repressor must be present. B. A corepressor must be present. C. RNA polymerase must bind to the promoter, and the repressor must be inactive. D. RNA polymerase cannot be present, and the repressor must be inactive.

They bind to receptors inside the cell and promote transcription of specific genes.

Which of the following processes do steroid hormones carry out to produce their effects? A. They activate translation of certain mRNAs. B. They activate key enzymes in metabolic pathways. C. They promote the breakdown of specific mRNAs. D. They bind to receptors inside the cell and promote transcription of specific genes.

They bind to other proteins or to a sequence element within the promoter called the TATA box.

Which of the following statements correctly describes the role of general transcription factors in eukaryotes? A. They bind to other proteins or to a sequence element within the promoter called the TATA box. B. They usually lead to a high level of transcription even without additional specific transcription factors. C. They are required for the expression of specific protein-encoding genes. D. They inhibit RNA polymerase binding to the promoter and begin transcribing.

DNA methylation reduces transcription, and histone acetylation promotes transcription.

Which of the following statements correctly describes the role of histone acetylation and DNA methylation in gene regulation? A. DNA methylation and histone acetylation both promote transcription. B. DNA methylation and histone acetylation both reduce transcription. C. DNA methylation promotes transcription, and histone acetylation reduces transcription. D. DNA methylation reduces transcription, and histone acetylation promotes transcription.

When allolactose is present, it induces the inactivation of the lac repressor.

Why is the lac operon said to be an inducible operon? A. When allolactose is present, it induces repression of gene expression. B. When allolactose is present, it induces the activation of the lac repressor. C. When activated, the lac operon induces repression of gene expression. D. When activated, the lac operon induces the production of lactose-digesting enzymes. E. When allolactose is present, it induces the inactivation of the lac repressor.

epigenome

a collection of all epigenetic changes in a genome

epigenetics

a field of study focused on changes in dna that don't involve alterations to the underlying sequence

histone acetylation

a histone modification where acetyl groups are attached to amino acids in histone tails. This loosens chromatin structures and promotes the initiation of transcription (turns genes on)

compressor

a molecule that cooperates with a repressor protein to switch an operon off

inducible operons

a type of negative gene regulation where the operon is off bcuz of an active repressor.

repressible operon

a type of negative gene regulation where the operon is on but can be inhibited by an active repressor

trp operon

a type of operon that is repressible and has genes that code for enzymes that are involved in trp synthesis

positive regulation

a type of regulation of gene transcription where an activator is needed to bind at the promoter in order to enable RNA polymerase to initiate transcription

negative regulation

a type of transcriptional regulation in bacteria where a repressor protein binds to an operator to prevent a gene from being expressed

positive regulation

a type of transcriptional regulation in bacteria where an activator is needed to bind at the promoter in order to enable the rna polymerase to initiate transcription

The lac operon

an operon that is an inducible operon and has genes that code for enzymes that function in the use of lactose

yes

can epigenetic modifications be reversed?

Operon model

gene expression in bacteria is controlled by a mechanism described by...

by a protein repressor that binds to the operator

how can the operon be switched off?

the binding of activators to control elements

in eukaryotes, the control of transcription depends on....

promoters, proximal control elements, and distal control elements

in eukaryotes, what are the 3 segments of dna that control transcription?

cell specialization

in multicellular organisms, regulation of gene expression is essential for...

off

is the lac operon on or off when lactose is absent?

on

is the operon on or off if the RNA polymerase can bind to the promoter

off

is the operon on or off when the RNA polymerase cannot bind to the promoter?

transcription factors

proteins that can bind to specific sequences on the dna and control gene expression

operon

the entire stretch of dna that includes the operator, the promoter, and the genes that they control

specific transcription factors

these are transcription factors that bind to control elements

general transcription factors

these are transcription factors that bind to other proteins or to a sequence element within the promoter called the TATA box

promoters

these signal the transcriptional start point. RNA polymerase binds to this

DNA methylation

this can impact the structure of chromatin as it is the addition of methyl groups to certain bases in dna, usually cytosine. This can condense chromatin and lead to reduced transcription

lactose

this is a disaccharide made of glucose and galactose. It's naturally found in milk, bacteria gets this from the environment and uses it as energy

differential gene expression

this is an expression of different genes by cells that have the same genome (some cells become brain cells, while others become heart cells etc.)

operator

this is known as the "switch" that can turn genes on and off and it's positioned within the promoter

repressor

this is the product of a regulatory gene

epigenetic inheritance

this is when the inheritance of traits is transmitted by mechanisms that are not directly involving the nucleotide sequence

alternative RNA splicing

this occurs when different mrna molecules are produced from the same primary transcript depending on which rna segments are treated as exons and which as introns

feedback inhibition and gene regulation

what are the 2 ways bacteria can regulate enzymes?

inducible and repressible operons

what are the two types of negative gene regulation?

positive and negative regulation of gene transcription

what are the two types of transcriptional regulation in bacteria?

general transcription factors and specific transcription factors

what are two types of transcription factors?

chemical modifications

what can influence chromatin structure and gene expression

to control enzyme activity

what does bacteria use feedback inhibition for?

to control the transcription of genes for enzymes

what does bacteria use gene regulation for?

to control the transcription of enzymes

what does bacteria use operons for?

the repressor

what does the inducer bind to

the structural genes are being transcribed

what happens when RNA polymerase binds to the promoter?

the structural genes are not transcribed

what happens when RNA polymerase cannot bind to the promoter?

the inducer

what inactivates the repressor?

dna and proteins (histones)

what is chromatin made of?

heterochromatin

what is highly condensed chromatin called?

euchromatin

what is less condensed chromatin called?

allolactose

what is the inducer that turns on the lac operon?

chromatin

what packs dna into a compact form and helps regulate gene expression?

inducers

what turns operons on?

an inducer that inactivates the repressor

what turns the lac operon on?

euchromatin

what type of chromatin comprises the most transcriptionally active part of the genome?

an inducible one

what type of operon is the lactose operon?

a repressible one

what type of operon is the trp operon?

chromatin

when a cell is not dividing, what do chromosomes appear as?

so it doesn't bind to the operator

why does the inducer bind to the repressor?