BIO 111- Chapter 15

A typical human cell expresses about what portion of its protein-coding genes at any given time?

20%

Which of the following would you expect to find as part of the receptor for a steroid hormone?

A domain that binds to DNA and domains that bind proteins

You have affixed a chromosome to a microscope slide. Which of the following would not make a good radioactively labeled probe to determine the presence of a particular gene on the chromosome?

A portion of the amino acid sequence of the gene's protein product

Which of the following mechanisms is used to coordinate the expression of multiple, related genes in eukaryotic cells?

A specific combination of control elements in each gene's enhancer coordinates the simultaneous activation of the genes.

In the control of gene expression in bacteria, a regulatory gene

All of the listed responses are correct.

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?

Allolactose binds to the repressor protein.

What allows for the more complex morphology of humans relative to those of simple invertebrates such as nematodes?

Alternative RNA splicing

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome. If she moves the promoter for the lac operon to the region between the beta galactosidase ( lacZ) gene and the permease ( lacY) gene, which of the following results would be likely?

Beta galactosidase will not be produced.

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome. If she moves the promoter for the lac operon to the region between the beta galactosidase (lacZ) gene and the permease (lacY) gene, which of the following results would be likely?

Beta galactosidase will not be produced.

Since Watson and Crick described the structure of DNA in 1953, which of the following statements might best explain why the function of small RNAs is still being explained?

Changes in technology as well as our ability to determine how much of the DNA is expressed have now made this possible.

What would occur if the repressor of an inducible operon mutated so that it could not bind the operator?

Continuous transcription of the operon's genes

Which of the following statements correctly describes the role of histone acetylation and DNA methylation in gene regulation?

DNA methylation reduces transcription, and histone acetylation promotes transcription.

Which of the following "genome-based" methods is useful for studying levels of gene expression in different tissues or different embryonic stages?

DNA microarray and RNA sequencing (RNA-seq)

Which of the following is not true of enhancers?

Each gene may have several enhancers, and each enhancer may be associated with and regulate several genes.

Gene expression might be altered based on post-transcriptional processing in eukaryotes rather than prokaryotes. Which of the following statements describes this difference?

Eukaryotic exons may be spliced in alternative patterns.

The operon model for the control of gene expression was discovered by which of the following?

Francois Jacob and Jacques Monod

Which of the following statements describes one of the functions of the protein called ubiquitin?

It attaches to proteins that are marked for destruction in the cell.

The tryptophan operon in some bacteria is a repressible operon. Which of the following statements correctly describes this operon?

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

Which of the following statements about the DNA in one of your brain cells is true?

It is the same as the DNA in one of your kidney cells.

Which statement about DNA in one of your brain cells is true?

It is the same as the DNA in one of your liver cells.

What effect does methylation have on DNA?

It makes it transcriptionally inactive.

Which of the following is NOT true of cDNA produced using human brain tissue as the starting material?

It was produced from pre-mRNA using reverse transcriptase.

Which of the following would not be true of cDNA produced using human brain tissue as the starting material?

It would contain sequences representing all the genes in the genome.

Which of the following events occurs during DNA replication?

Methylation of the DNA is maintained because methylation enzymes act at DNA sites where one strand is already methylated and thus correctly methylate daughter strands after replication.

Which of the following statements explains why a larger portion of the DNA in a human cell is transcribed than would be predicted by the 1.5% of the genome that is protein-coding DNA?

Much of the non-protein-coding RNA functions to regulate the translation or degradation of mRNAs.

Which of the following is not an example of the control of gene expression after transcription?

Multiple copies of an rRNA gene are present throughout the genome.

Could you use cDNA produced from a fertilized egg to build a DNA microarray "chip" for the entire genome of the organism?

No, because cDNA is produced using the mRNA that a cell is producing, and no cell expresses all its genes at the same time.

Which of the following must occur in order for a repressible operon to be transcribed?

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

Which of the following techniques involves reverse transcriptase, PCR amplification, and gel electrophoresis?

RT-PCR

It is possible for a cell to make proteins that last for months; hemoglobin in red blood cells is a good example. However, many proteins are not this long-lasting; they may be degraded in days, hours, or even minutes. What is the advantage of short-lived proteins?

Short-lived proteins enable the cells to control their activities precisely and efficiently.

DNA sequences can act as "tape measures of evolution". Some highly conserved regions of the human genome (similar to comparable regions in other species) don't code for proteins. Why?

Such regions play a significant role in gene regulation. That is why they remain conservative under the influence of natural selection.

A researcher introduces double-stranded RNA into a culture of mammalian cells. The double-stranded RNA corresponds to a region of a protein-coding gene of interest. How may the introduced RNA affect gene expression in these cells?

The amount of protein produced by the target gene may be significantly reduced.

Which of the following environments would most likely lead to the transcription of the lactose operon?

The cyclic AMP and lactose levels are both high within the cell.

How is the coordinated transcription of all the genes involved in a particular metabolic pathway brought about in eukaryotes?

The genes all have the same combination of control elements in their enhancers.

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome. If she moves the regulatory gene ( lac I), along with its promoter, to a position some several thousand base pairs away from its normal position, which would you expect to occur?

The lac operon will function normally.

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome. If she moves the regulatory gene (lac I), along with its promoter, to a position some several thousand base pairs away from its normal position, which would you expect to occur?

The lac operon will function normally.

Which of the following statements correctly describes the role of a molecule that controls a repressible operon?

The molecule binds to the repressor protein and activates it.

Which of the following is an example of post-transcriptional control of gene expression?

The removal of introns and alternative splicing of exons

A type of mutation in bacteria in the repressor results in a molecule known as a super-repressor because it represses the lac operon permanently. Which of the following processes would occur in such a mutant?

The repressor protein cannot bind the inducer.

Which of the following is an example of positive regulation of gene expression in E. coli?

The role of cyclic AMP in regulation of the lac operon

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome. If she moves the operator to the far end of the operon, past the transacetylase ( lacA) gene, which of the following results would likely occur when the cell is exposed to lactose?

The three genes of the operon will be transcribed continuously.

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome. If she moves the operator to the far end of the operon, past the transacetylase (lacA) gene, which of the following results would likely occur when the cell is exposed to lactose?

The three genes of the operon will be transcribed continuously.

Which of the following results can a DNA microarray assay detect or identify?

They allow the expression of many or even all of the genes in a genome to be compared at once.

Which of the following statements correctly describes the role of general transcription factors in eukaryotes?

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

Which of the following processes do steroid hormones carry out to produce their effects?

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

Why is the lac operon said to be an inducible operon?

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

You are given an experimental problem involving control of a gene's expression in the embryo of a particular species. One of your first questions is whether the gene's expression is controlled at the level of transcription or translation. Which of the following experiments might best give you an answer?

You measure the quantity of the appropriate pre-mRNA in various cell types and find they are all the same.

Researchers are looking for better treatments for breast cancer. For a particular DNA microarray assay (DNA chip), cDNA has been made from the mRNAs of a dozen patients' breast tumor biopsies. What would the researchers be looking for in this type of assay?

a pattern shared among some or all of the samples that indicates gene expression differing from control samples

Which of the following statements best describes siRNA?

a short double-stranded RNA, one of whose strands can block gene expression

Altering patterns of gene expression in prokaryotes would most likely contribute to the organism's survival in which of the following ways?

allowing the organism to adjust to changes in environmental conditions

Which of the following activities can prokaryotes carry out in response to certain chemical signals?

alter the level of production of various enzymes

A eukaryotic gene is typically associated with all of the following except

an operator

Inducible enzymes______

are produced when a molecule inactivates a repressor protein

In E. coli, tryptophan switches off the trp operon by

binding to the repressor and increasing its affinity for the operator

How do miRNAs function in controlling gene expression?

by binding to mRNAs and degrading them or blocking their translation

Which of the following is not a post-transcriptional stage of gene regulation?

chromatin modification

What would be the result of a mutation that deactivates the regulatory gene of a repressible operon in an Escherichia coli cell?

continuous transcription of the enzyme-coding gene controlled by that regulator

A mutation that renders the product of a regulatory gene for a repressible operon nonfunctional would result in

continuous transcription of the genes of the operon

What would occur if the repressor of an inducible operon were mutated so it could NOT bind the operator?

continuous transcription of the operon's genes

What would occur if the repressor of an inducible operon were mutated so it could not bind the operator?

continuous transcription of the operon's genes

A lack of which of the following molecules would result in the cell's inability to "turn off" genes?

corepressor

In positive control of several sugar-metabolism-related operons, the cAMP receptor protein (CRP) binds to DNA to stimulate transcription. Which of the following events activates CRP?

decrease in glucose and increase in cAMP

A researcher found a method she could use to manipulate and quantify acetylation in embryonic cells in culture. In one set of experiments using this procedure in Drosophila, she was readily successful in increasing acetylation of amino acids in histone tails. Which of the following results would she most likely see?

decreased chromatin condensation

A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture. In one set of experiments she succeeded in decreasing methylation of histone tails. Which of the following results would she most likely see?

decreased chromatin condensation

Control elements located far from the genes they regulate are also called

distal control elements or enhancers

The control of gene expression is more complex in eukaryotic cells than prokaryotic cells because

eukaryotic DNA is packaged with proteins in an elaborate complex

Which of the following chemical modifications leads to condensation of chromatin and therefore reduces levels of transcription?

histone methylation and DNA methylation

Attachment of acetyl groups to __________ promotes transcription.

histone tails

DNA methylation is a mechanism used by eukaryotes to

inactivate genes

Most repressor proteins exhibit allosteric properties. Which of the following molecules binds with the repressor to alter its structure?

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?

inducer

How does an abundance of tryptophan inhibit the production of more tryptophan?

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

Name the starting molecule from which cDNA is synthesized and the enzyme that carries out the synthesis.

mRNA ... reverse transcriptase

DNA methylation of cytosine residues

may be a mechanism of epigenetic inheritance when methylation patterns are repeated in daughter cells

At the beginning of this century there was a general announcement regarding the sequencing of the human genome and the genomes of many other multicellular eukaryotes. There was surprise expressed by many that the number of protein-coding sequences in the human genome was much smaller than had been expected. Which of the following statements would describe most of the rest of the DNA in the human genome?

non-protein-coding DNA that is transcribed into several kinds of small RNAs with biological function

In the microarray shown in the figure above, if you were searching for genes whose expression was inhibited by hormone treatment, you would search for sequences spotted on the array that showed what level of fluorescence?

none

Transcription factors in eukaryotes usually have DNA-binding domains as well as other domains that are specific for binding other molecules. In general, which of the following would you expect many of them to be able to bind?

other transcription factors

Among the newly discovered small noncoding RNAs, one type reestablishes methylation patterns during gamete formation and blocks expression of some transposons. What are these types of RNA called?

piRNA

Which of the following is a protein product of a regulatory gene?

repressor

Gene expression can be blocked by a process called RNA interference. Which of the following molecules is involved in this process?

siRNAs

One way scientists hope to use the recent knowledge gained about noncoding RNAs lies with the possibilities for their use in medicine. Of the following scenarios for future research, which would you expect to gain most from RNAs?

targeting siRNAs to disable the expression of an allele associated with an autosomal dominant disease

If a particular operon encodes enzymes for making an amino acid and is regulated like the trp operon, then

the amino acid acts as a corepressor

If a particular operon encodes enzymes for making an essential amino acid and is regulated like the trp operon, then

the amino acid acts as a corepressor

In a genome-wide expression study using a DNA microarray assay, what is each spot used to detect?

the expression of a specific gene by a cell

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 with male sexual characteristics. What is the function of these proteins?

to help RNA polymerase transcribe certain genes

When the substrate of a metabolic pathway is present in a bacterial cell, which of the following processes will occur?

transcription of the genes in an inducible operon

The functioning of enhancers is an example of

transcriptional control of gene expression