Deck 36: Transcription: RNA Synthesis, Processing, and Regulation

Question 1

You are studying lipoprotein processing in a strain of mutant mice. You find that these mice synthesize the same apolipoprotein composition contained in lipoproteins made in the liver and the intestines, whereas, in wild-type mice there are 2 different sized apolipoproteins in these same tissues. Examination of the mRNA processing in the mutant mice would most likely show a defect in which of the following processes?

A) alternative polyadenylation
B) alternative splicing
C) differential capping
D) posttranscriptional modification converting a U to a T residue
E) RNA editing

Answer 1

RNA editing

Question 2

You are studying the processes of RNA transcription in a cell-free system. You find that although the RNA polymerase II in your system initiates transcription as expected, it does not complete the process. Which of the following modifications to the enzyme is most likely not taking place, thereby, explaining the lack of complete transcription?

A) 5′ capping
B) acetylation
C) methylation
D) phosphorylation
E) ubiquitination

Answer 2

phosphorylation

Question 3

Which of the following represents a characteristic feature of the cap structure on the 5′ end of most eukaryotic mRNAs?

A) it is a methylated adenine
B) it is a methylated cytidine
C) it is a methylated guanine
D) it is an adenine found attached to a cytidine dinucleotide in the context A-C-C
E) it is a guanine found attached to a cytidine dinucleotide in the context G-C-C

Answer 3

it is a methylated guanine

Question 4

You are comparing the process of RNA splicing in an mRNA from normal and mutant cells of the same tissue. You find that the mutant mRNA is longer than the mRNA from the normal cells. Examination of the sequences of the gene encoding this mRNA reveals that there are nucleotide changes at the boundary of one of the exons in the mutant cell gene. Which of the following nucleotides would be expected to be found at the 3′ end of upstream donor exons and the 5′ end of downstream acceptor exons in the normal gene but not in the mutant gene?

A) AG-G
B) AG-AG
C) CA-GA
D) CG-G
E) G-AG

Question 5

Which of the following relates to the transcription of a eukaryotic mRNA gene?

A) begins only when repressors are removed from nucleosomes in which the gene lies
B) occurs when the gene is in heterochromatin
C) requires binding of RNA polymerase II to the CCAAT box
D) requires binding of TFIID to the TATA box
E) requires eIF-2

Question 6

You are examining the process of RNA synthesis in a cell line derived from a pancreatic tumor. You discover that the cells do not contain any U1 small nuclear RNA (snRNA). The lack of this RNA species in these cells is most likely to have which of the following effects on overall RNA synthesis?

A) defective polyA tail addition
B) failure of capping mRNAs
C) loss of intron splicing
D) no synthesis of any mRNAs
E) synthesis of only rRNAs

Question 7

The process of RNA editing leads to sequence changes that are not reflective of the genetic information contained within the gene for an edited RNA. RNA editing occurs through the action of specific nucleotide deaminases that change either adenine to inosine or cytidine to uridine. These nucleotide changes can affect the coding or splicing capacity of the RNA. Which of the following proteins is an important example of the result of RNA editing?

A) apo-B48
B) calcitonin gene related peptide (CGRP)
C) ferritin
D) glutamate dehydrogenase
E) tissue factor (factor III)

Question 8

If the DNA strand shown below is used as a template for RNA polymerase, what would be the sequence of the resultant mRNA following transcription?
5′-CATTCCATAGCATGT-3′

A) 5′-ACAUGCUAUGGAAUG-3′
B) 5′-CAUUCCAUAGCAUGU-3′
C) 5′-GUAAGGUAUCGUACA-3′
D) 5′-UGUACGAUACCUUAC-3′

Question 9

A mutation that resulted in the loss of histone deacetylation activity in a eukaryotic cell line would be expected to have what effect on transcription?

A) conversion of activators into repressors
B) conversion of repressors into activators
C) enhanced rate of transcription
D) no effect
E) reduced rate of transcription

Question 10

Which of the following best describes the role of proteins that contain a basic helix-loop-helix (bHLH) domain, such as in the MyoD protein involved in the determination of muscle lineages?

A) binds to specific regions of DNA
B) interacts with the splicesome
C) participates in the polyadenylation of mRNAs
D) participates in the splicing of mRNAs
E) promotes the transnuclear transport of processed mRNAs

Question 11

Which of the following is the sequence of the DNA strand that serves as the template strand for transcription of the following strand of RNA?
RNA: 5′-AAGCGUUUGGG-3′

A) 3′-AAGCGTTTGGG-5′
B) 5′-AAGCGTTTGGG-3′
C) 5′-CCCAAACGCTT-3′
D) 5′-GGGTTTGCGAA-3′
E) 5′-TTCGCAAACCC-3′

Question 12

You are studying RNA processing in a cell-free system. You find that incomplete RNA processing is occurring in your system and that the failure is most likely due to incomplete assembly of the splicesome complex. Which of the following RNA-processing events is most likely defective in your assay system?

A) addition of poly(A)
B) guiding ribosomes to the endoplasmic reticulum
C) modification of the 5′ end of hnRNA
D) removal of introns in hnRNA
E) transport of mRNA to the cytoplasm

Question 13

You have developed a strain of transgenic mice that express a human β-globin gene. Your transgenic construct includes all 3 exons of the human β-globin gene plus 500 nucleotides of both 5′- and 3′-flanking sequences. Examination of these transgenic mice shows that the human β-globin construct is expressed at levels about 10-fold lower than the endogenous mouse β-globin gene. Which of the following regulatory elements is most likely missing from your transgenic construct, thereby explaining the reduced level of expression?

A) enhancer elements
B) mRNA splicing signals
C) polyadenylation signals
D) promoter elements
E) silencer elements

Question 14

The completion of the human genome project demonstrated that the human genome codes for approximately 25,000 genes. However, these limited numbers of genes actually encode several hundreds of thousands of different proteins. Which of the following processes provides the majority of the additional diversity of the protein products from these genes?

A) DNA transposition
B) mRNA splicing
C) mutagenesis
D) rRNA processing
E) tRNA modification

Question 15

Many members of the nuclear family of receptors are prevented from activity through protein-protein interaction. The glucocorticoid receptor, for example, is released from hsp90 (a chaperone protein) following binding by the appropriate steroid hormone. Which of the following represents the next event for the localization of the receptor-hormone complex?

A) cytoplasmic surface of the plasma membrane
B) Golgi cisterna
C) specific DNA sequences
D) specific mRNA transcripts
E) 50S ribosomal subunit

Question 16

You are characterizing the expression of a gene suspected of causing a form of ovarian cancer. You have isolated the gene and found that it is approximately 35 kilobases (kb) in length. Transcriptional analysis reveals that there are several discrete mRNAs produced by this gene ranging in length from 2.0 to 5.5 kb in normal and cancerous cells. Which of the following processes is the most likely cause of the difference in size of the mRNAs produced by this gene?

A) poly(A) addition
B) posttranslational modification
C) recombination
D) RNA editing
E) splicing

Question 17

You are studying the activities of the apolipoproteins, apoB-48 and apoB-100. Both of these proteins are encoded by the same gene; yet apoB-48 is primarily expressed in the intestine, while apoB-100 expression is restricted to the liver. Which of the following is the most likely molecular process accounting for this difference in gene expression?

A) different initiation codons
B) DNA methylation
C) gene duplication
D) reiterated sequences
E) RNA editing

Question 18

You are isolating and characterizing the nucleic acids from a variety of different cell types. You fractionate and hydrolyze a specific sample of the nucleic acids. You find that the sample being analyzed contains pseudouridine. Which of the following is the most likely nucleic acid you have analyzed?

A) DNA
B) mtDNA
C) mRNA
D) rRNA
E) tRNA

Question 19

You are carrying out experiments designed to characterize the structure-function relationships of tRNAs. You isolate an enzyme with tRNA nucleotidyltransferase activity and show that it adds a CCA sequence to the 3′ end of human tRNAs. Which of the following characteristics best distinguishes this enzyme from other RNA polymerases?

A) requires only a GG template
B) synthesizes a specific sequence without a template
C) uses both mRNA and tRNA as substrates
D) uses nucleoside monophosphate as substrates
E) works in a 3′→5′ direction

Question 20

You are studying the rRNA synthesis and processing in a mutant cell line. You find that these cells synthesize a correct precursor rRNA, but do not correctly process it into the expected 3 rRNAs that are found in normal cells. Which of the following organelles is likely to be missing or defective in these cells, thus accounting for the failed rRNA processing?

A) endoplasmic reticulum
B) Golgi complex
C) nuclear matrix
D) nucleolus
E) ribosome

Question 21

You are treating cultured cells with an experimental compound. You find that addition of the compound results in a 2-fold increase in the expression of a specific gene. However, you find that the addition of the test compound causes a 10-fold increase in the level of the protein derived from the gene. The major effect of this experimental compound is most likely to be a decrease in which of the following?

A) degradation of mRNA by nucleases
B) rate of mRNA translation
C) rate of ribosomes binding to mRNA
D) RNA polymerase II activity
E) splicing of nascent RNA transcripts

Question 22

A transcriptional promoter is required for which of the following processes?

A) cleavage and polyadenylation of mRNA
B) initiation of RNA synthesis
C) recognition of the 3′ boundary for mRNA splicing
D) recognition of the 5′ boundary for mRNA splicing
E) termination of RNA synthesis

Question 23

The most common mechanism for the regulated expression of human genes during fetal development occurs at which of the following levels?

A) degradation of the protein product
B) excision of introns from precursor RNA
C) initiation of protein synthesis
D) initiation of RNA synthesis
E) modification of the newly synthesized protein

Question 24

Transcription factor proteins bind to specific DNA sequences present in their target genes. These factors subsequently lead to increased transcription of target genes by which of the following processes?

A) blocking the effects of repressor molecules
B) bringing RNA nucleotides into contact with the DNA template
C) increasing the rate of initiation
D) increasing the speed of RNA polymerase transcription
E) preventing the pausing of RNA polymerase along the DNA template

Question 25

Which of the following mechanisms inhibits expression of imprinted genes?

A) capping of the genes' mRNA
B) deletion of the gene's promoter region
C) dissociation of RNA pol II from the gene
D) inhibition of mRNA splicing
E) methylation of cytosine residues within the gene

Question 26

You are studying the changes that have occurred in the genomes of members of a family susceptible to an inherited form of liver cancer. You find that afflicted family members harbor a mutation in the zinc-finger motif of a cell-cycle regulatory gene. Which of the following is the most likely result of this mutation?

A) decreased binding of a transcription factor to a DNA sequence
B) enhanced binding of hormones to receptors
C) enhanced transport of a hormone receptor complex into the nucleus
D) stimulation of mRNA synthesis
E) "unzipping" of leucine-rich helices

Question 27

Homeobox (HOX) genes play a role in controlling events of embryogenesis. These genes exert their functions through which of the following processes?

A) allelic exclusion
B) alternate mRNA splicing
C) regulation of transcription
D) regulation of translation
E) signal transduction

Question 28

Classically it was considered that each gene encoded one protein, the so-called one gene-one enzyme hypothesis. However, this model was modified as a result of the discovery of which of the following?

A) alternative splicing of primary transcripts to produce different forms of a protein
B) enhancer elements located upstream or downstream of the transcriptional promoter site in the DNA
C) oncogene products that act as transcription factors
D) transcription attenuation that regulates gene expression
E) variable number tandem repeats generating alternative processed genes during meiosis

Question 29

All cells contain the same compliment of DNA. However, adipose tissue cells and gastrointestinal epithelial cells are not composed of the same proteins. The differences in these cells, as well as all other cells, is most likely a result of differences in which of the following?

A) DNA sequences
B) mRNAs
C) quantity of DNA in their nuclei
D) rRNAs
E) tRNAs

Question 30

You are studying the effects of exposure of mouse embryos to various concentration of retinoic acid. Your studies show that the developmental malformations you observe are due to retinoic acid-induced changes in the expression of several homeobox (HOX) genes. Both retinoic acid receptors and HOX gene products recognize and bind to specific DNA sequences at numerous sites on multiple chromosomes. Which of the following best describes the function of these molecules?

A) initiation factors
B) ligands
C) polymerases
D) signal recognition particles
E) transcription factors