Chapter 20 Mastering Biology

regulatory gene

codes for a protein, such as a repressor, that controls the transcription of another gene or group of genes

Genes associated with embryonic development are known as

homeotic genes

You are examining a bacterial enzyme associated with glycolysis. You would expect expression of the enzyme to be

induced by glucose

The operon model of the regulation of gene expression in bacteria was proposed by

Jacob and Monod

In eukaryotic cells, which of the following genetic elements can prevent the increase in gene expression that results from the presence of an enhancer sequence?

insulator

genes of an operon

is/are arranged sequentially after the promoter

In the presence of a regulatory protein the lac operon is

not transcribed

The genes responsible for catabolism of the amino acid methionine in bacteria are not transcribed or translated in the absence of methionine. When methionine is added to the bacteria, genes for methionine are turned on. Which of the following is the likely scenario for initiation of transcription of methionine transcription genes? Methionine is a subunit of RNA polymerase that acts as a sigma factor. Methionine binds to the DNA to serve as a binding site for RNA polymerase. Methionine is binding to a steroid receptor in the nucleus. Methionine is an inducer that binds to a genetic repressor protein.

Methionine is an inducer that binds to a genetic repressor protein

Which of the following terms describes the DNA-protein complexes that look like beads on a string?

Nucleosome The "beads on a string" appearance of nucleosomes comes from the wrapping of DNA around a core of eight histone proteins.

Which of the following events in transcription initiation likely occurs last?

RNA polymerase binds to the promoter of the gene. RNA polymerase is recruited only when other transcription factors, including TBP, are assembled at the promoter.

What is the function of a spliceosome?

RNA processing Spliceosomes are involved in RNA processing.

Which of the following processes is/are associated with the modification of histone proteins in vivo? alkylation methylation acetylation and methylation acetylation transhydroxylation

acetylation and methylation

In eukaryotes, post-transcriptional control of gene regulation may involve

alternative mRNA splicing, control of nuclear export of mRNAs to the cytoplasm, and differential mRNA degradation

Bacteria that use the lac operon are grown in a laboratory under conditions of high lactose and no glucose. A researcher then adds progressively more and more glucose to the bacteria. Which of the following describes the temporal changes the bacteria experience in this experiment? cAMP levels will rise and expression of the lac operon will decrease as a function of time in the experiment. cAMP levels will rise and expression of the lac operon will increase as a function of time in the experiment. cAMP levels will fall and expression of the lac operon will decrease as a function of time in the experiment. cAMP levels will remain constant and expression of the lac operon will increase as a function of time in the experiment.

cAMP levels will fall and expression of the lac operon will decrease as a function of time in the experiment.

Enzymes that add ubiquitin to proteins have been found in the nucleus of eukaryotic cells. These enzymes would be most likely to regulate gene expression by

causing degradation of transcription factors and changing which genes are expressed

Regulatory proteins bind to the _______ to control expression of the operon

operator

Which of the following regulatory elements is not composed of DNA sequences?

Activators Activators are proteins that are involved in transcription initiation.

Effector molecules are associated with the repression of enzyme synthesis. are associated with the induction of enzyme synthesis. induce conformational changes. are often small organic molecules. All of these are true.

All of these are true

A eukaryotic gene is observed to make multiple forms of a protein. How can one eukaryotic gene produce multiple products in the same cell?

Alternative splicing sites can lead to the production of two different mature mRNAs from the same gene, resulting in slightly different proteins

Which of the following regulatory DNA sequences might be located thousands of nucleotides away from the transcription start site of a gene?

Enhancers Enhancers can function thousands of nucleotides away from the promoter and transcription start site.

True or false? Regulatory and basal transcription factors regulate transcription by binding to the promoter.

False Basal transcription factors do indeed bind to the promoter, but regulatory transcription factors bind to promoter-proximal elements and enhancers.

True or false? One possible way to alter chromatin structure such that genes could be transcribed would be to make histone proteins more positively charged.

False The positive charge on histone proteins allows them to interact tightly with negatively charged DNA, thus inhibiting transcription. To disrupt this interaction, the histone proteins would have to be made more negatively charged.

The situation in which an active regulatory protein "turns on" gene expression is an example of

positive control

Protein phosphorylation, protein folding, and proteolytic cleavage are all examples of

post-translational control of gene expression and activity

Enzyme complexes that break down protein are called

proteasomes Proteasomes are enzyme complexes that break down proteins.

Protein-phosphorylating enzymes' role in the regulation of gene expression involves

protein activation Proteins are often activated by phosphorylation.

repressor

protein that inhibits gene transcription. In prokaryotes, this protein binds to the DNA in or near the promoter

The nuclear membrane's role in the regulation of gene expression involves

regulating the transport of mRNA to the cytoplasm This is the role of the nuclear membrane in the regulation of gene expression.

Which of these is NOT a component of the lac operon?

regulatory gene only

You are examining an enzyme associated with cysteine biosynthesis. You would expect expression of the enzyme to be

repressed by cysteine

One mechanism that may lead to novel disease treatment involves ________, which hinders the translation of specific mRNAs

siRNA

promoter

specific nucleotide sequence in DNA that binds RNA polymerase, positioning it to start transcribing RNA at the appropriate place

inducer

specific small molecule that binds to a bacterial regulatory protein and changes its shape so that it cannot bind to an operator, thus switching an operon on

operon

stretch of DNA consisting of an operator, a promoter, and genes for a related set of proteins, usually making up an entire metabolic pathway

Regulatory proteins bind to

the operator

If the gene encoding the lac repressor is mutated so that the repressor can no longer bind the operator, will a high level of transcription of that operon occur?

yes, because RNA polymerase will be able to bind the promoter and transcribe the operon