Bio Chapter 15

Gene expression might be altered based on post-transcriptional processing in eukaryotes rather than prokaryotes because of which of the following? A. Eukaryotic exons may be spliced in alternative patterns. B. Prokaryotes use ribosomes of different structure and size. C. Prokaryotic genes are expressed as mRNA, which is more stable in the cell. D. Eukaryotic mRNAs get 5' caps and 3' tails.

A. Eukaryotic exons may be spliced in alternative patterns.

A type of mutation in the repressor results in a molecule known as a super-repressor because it represses the lac operon permanently. Which of these would characterize such a mutant? A. It cannot bind to the inducer. B. It makes molecules that bind to one another. C. It cannot make a functional repressor. D. It cannot bind to the operator.

A. It cannot bind to the inducer.

In a genome-wide expression study using a DNA microarray assay, what is each well used to detect? A. expression of a specific gene by a cell B. fate of proteins produced by a cell C. location of a protein produced by a cell D. location of a gene within a cell

A. expression of a specific gene by a cell

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 could account for most of the rest of the DNA in the human genome? A. non-protein-coding DNA that is transcribed into several kinds of small RNAs with biological function B. non-protein-coding DNA that is transcribed into several kinds of small RNAs without biological function C. "junk" DNA that serves no possible purpose D. DNA that is translated directly without being transcribed E. rRNA and tRNA coding sequences

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

Which of the following is an example of post-transcriptional control of gene expression? A. the removal of introns and alternative splicing of exon B. the binding of transcription factors to a promoter C. the binding of RNA polymerase to transcription factors D. the addition of methyl groups to cytosine bases of DNA

A. the removal of introns and alternative splicing of exon

How have DNA microarrays had such a huge impact on genomic studies? A. They can be used to introduce entire genomes into bacterial cells. B. They allow the expression of many or even all of the genes in a genome to be compared at once. C. They allow physical maps of the genome to be assembled in a very short time. D. They can identify the function of any gene in a genome.

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

Which of the following mechanisms is used to coordinate the expression of multiple, related genes in eukaryotic cells? A. The genes share a single common enhancer, which allows appropriate activators to turn on their transcription at the same time. B. A specific combination of control elements in each genes enhancer coordinates the simultaneous activation of the genes. C. The genes are organized into large operons, allowing them to be transcribed as a single unit. D. A single repressor is able to turn off several related genes. E. Environmental signals enter the cell and bind directly to promoters

B. A specific combination of control elements in each genes enhancer coordinates the simultaneous activation of the genes.

Gene expression can be blocked by small RNA molecules called siRNAs. What is this process called? A. RNA targeting B. RNA interference C. RNA disposal D. RNA blocking

B. RNA interference

Which statement(s) about repressible operons is/are correct? Select all that apply. A. In a repressible operon, the repressor is synthesized in an active form. B. Repressible operons usually contain genes that code for anabolic enzymes. C. A repressible operon is on unless a corepressor is present.

B. Repressible operons usually contain genes that code for anabolic enzymes. C. A repressible operon is on unless a corepressor is present.

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? A. Most cells have a short life span. B. Short-lived proteins enable the cells to control their activities precisely and efficiently. C. Cells lack the raw materials to make most of the proteins they need. D. Long-lasting proteins are likely to make the cell cancerous. E. Most proteins are used only once.

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

In eukaryotes, general transcription factors A. usually lead to a high level of transcription even without additional specific transcription factors. B. bind to other proteins or to a sequence element within the promoter called the TATA box. C. inhibit RNA polymerase binding to the promoter and begin transcribing. D. are required for the expression of specific protein-encoding genes. E. bind to sequences just after the start site of transcription.

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

In positive control of several sugar-metabolism-related operons, the cAMP receptor protein (CRP) binds to DNA to stimulate transcription. What causes an increase in CRP? A. increase in glucose and decrease in cAMP B. decrease in glucose and increase in cAMP C. decrease in glucose and increase in repressor D. increase in glucose and increase in cAMP E. decrease in glucose and decrease in repressor

B. decrease in glucose and increase in cAMP

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

B. inactivate genes

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. corepressor B. inducer C. promoter D. ubiquitin E. repressor

B. inducer

The functioning of enhancers is an example of __________. A. the stimulation of translation by initiation factors B. transcriptional control of gene expression C. a eukaryotic equivalent of prokaryotic promoter function D. post-translational control that activates certain proteins

B. transcriptional control of gene expression

Two potential functions that eukaryotic cells perform to regulate transcription are A. DNA amplification and histone methylation. B. histone amplification and DNA acetylation. C. DNA methylation and histone modification. D. DNA methylation and histone amplification. E. DNA acetylation and methylation.

C. DNA methylation and histone modification.

Which statement about DNA in one of your brain cells is true? A. The majority of genes are likely to be transcribed. B. Many genes are grouped into operon-like clusters. C. It is the same as the DNA in one of your liver cells. D. Most of the DNA codes for protein.

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

Which of the following would NOT be true of cDNA produced using human brain tissue as the starting material? A. It could be amplified by the polymerase chain reaction. B. It lacks the introns of the pre-mRNA. C. It was produced from pre-mRNA using reverse transcriptase. D. It could be labeled and used as a probe to detect genes expressed in the brain.

C. It was produced from pre-mRNA using reverse transcriptase.

For a repressible operon to be transcribed, which of the following must occur? A. A corepressor must be present. B. RNA polymerase and the active repressor 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.

C. 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? A. DNA microarray assays B. nucleic acid hybridization C. RT-PCR D. in situ hybridization

C. RT-PCR

Which of the following environments would most likely lead to the transcription of the lactose operon? A. The cyclic AMP levels are low. B. There is glucose but no lactose in the cell. C. The cyclic AMP and lactose levels are both high within the cell. D. There is more glucose in the cell than lactose. E. The cAMP level is high and the lactose level is low.

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

A gene on human chromosome 15 is expressed throughout the body. However, in the brain, only the maternal copy of the gene is expressed, whereas the paternal copy of the gene is silent and not transcribed. What accounts for this pattern of expression this gene displays in the brain? A. The copies of this gene in brain cells are coordinately controlled with the copies of the gene in body cells. B. In the brain, the maternal copy of the gene is methylated whereas the paternal copy is un-methylated. C. Through genomic imprinting, methylation regulates expression of the paternal copy of the gene in the brain

C. Through genomic imprinting, methylation regulates expression of the paternal copy of the gene in the brain

What would be the result of a mutation that deactivates the regulatory gene of a repressible operon in an Escherichia coli cell? A. continuous translation of the mRNA because of alteration of its structure B. inactivation of RNA polymerase by alteration of its active site C. continuous transcription of the structural gene controlled by that regulator D. complete inhibition of transcription of the structural gene controlled by that regulator E. irreversible binding of the repressor to the operator

C. continuous transcription of the structural gene controlled by that regulator

If a particular operon encodes enzymes for making an essential amino acid and is regulated like the trp operon, then __________. A. the amino acid turns on transcription of the operon B. the amino acid inactivates the repressor C. the amino acid acts as a corepressor D. the repressor is active in the absence of the amino acid

C. the amino acid acts as a corepressor

Which of the following events occurs during DNA replication? A. All methylation of the DNA is lost at the first round of replication. B. DNA polymerase is blocked by methyl groups, and methylated regions of the genome are therefore left uncopied. C. Methylated DNA is copied in the cytoplasm, and unmethylated DNA is copied in the nucleus. D. 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. E. Methylation of the DNA is maintained because DNA polymerase directly incorporates methylated nucleotides into the new strand opposite any methylated nucleotides in the template.

D. 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.

Transcription of the genes in an inducible operon A. begins when the product of the metabolic pathway is present. B. occurs continuously in the cell. C. increases when the product of the metabolic pathway is present. D. begins when the substrate of the metabolic pathway is present.

D. begins when the substrate of the metabolic pathway is present.

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

D. corepressor

Name the starting molecule from which cDNA is synthesized and the enzyme that does the synthesis. A. HIV ... RNA polymerase B. tRNA ... RNA polymerase C. DNA ... DNA polymerase D. mRNA ... reverse transcriptase E. mRNA ... DNA polymerase

D. mRNA ... reverse transcriptase

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? A. repressors B. tRNA C. protein-based hormones D. other transcription factors

D. other transcription factors

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

D. to help RNA polymerase transcribe certain genes

The tryptophan operon in some bacteria is a repressible operon that is A. turned on only when glucose is present in the growth medium. B. permanently turned on. C. turned off whenever tryptophan is added to the growth medium. D. turned on only when tryptophan is present in the growth medium. E. turned off only when glucose is present in the growth medium.

D. turned on only when tryptophan is present in the growth medium.

Since Watson and Crick described DNA in 1953, which of the following statements might best explain why the function of small RNAs is still being explained? A. Watson and Crick described DNA but did not predict any function for RNA. B. As RNAs have evolved since that time, they have taken on new functions. C. The functions of small RNAs could not be approached until the entire human genome was sequenced. D. Ethical considerations prevented scientists from exploring this material until recently. E. Changes in technology as well as our ability to determine how much of the DNA is expressed have now made this possible

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

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. a pattern of fluorescence that indicates which cells are overproliferating B. a group of cDNAs that act differently from those on the rest of the grid C. a group of cDNAs that match those in non-breast-cancer control samples from the same population D. a particular gene that is amplified in all or most of the patient samples E. a pattern shared among some or all of the samples that indicates gene expression differing from control samples

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

If you were to observe the activity of methylated DNA, you would expect it to A. be replicating nearly continuously. B. be unwinding in preparation for protein synthesis. C. induce protein synthesis by not allowing repressors to bind to it. D. be very actively transcribed and translated. E. be transcriptionally inactive.

E. be transcriptionally inactive.

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

E. repressor