E. coli preferentially utilize glucose for energy. However, in the absence of glucose, genes that can metabolize alternative sugars are activated. Low glucose
a. activates the i gene that subsequently activates the lac operon, allowing energy to be derive
c
Transcription in Prokaryotes
Which of the following statements about transcriptional termination in prokaryotes is false?
a. Termination is signaled by a GC-rich interval that forms a stem-loop structure in the RNA.
b. Transcription terminates when the RNA polymerase dissociates from
Correct Answer: c
Answer A Feedback: Incorrect. This is a true statement.
Textbook Reference: Transcription in Prokaryotes
Suppose that a gene has three exons and two introns in the following order: 5? exon 1 - intron 1 - exon 2 - intron 2 - exon 3 3?. Which of the following could not result from alternative splicing in this gene?
a. 5? exon 1 - exon 2 - exon 3 3?
b. 5? exon
Correct Answer: c
Your Answer: c
Answer C Feedback: Correct! Although the process of alternative splicing can change the identity of the exons in the mature mRNA, it does not alter the order of exons.
Textbook Reference: RNA Processing and Turnover
According to the central dogma of molecular biology, transcription of genetic information occurs via
a. DNA-dependent DNA synthesis.
b. DNA-dependent RNA synthesis.
c. RNA-dependent DNA synthesis.
d. RNA-dependent protein synthesis.
Correct Answer: b
Your Answer: d
Answer D Feedback: Incorrect. That is called translation.
Textbook Reference: Introduction
Which of the following is not involved in the tissue-specific expression of the immunoglobin (Ig) heavy-chain gene?
a. Its enhancer
b. Transcriptional activators
c. Transcriptional repressors
d. RNA polymerase II
Correct Answer: d
Your Answer: a
Answer A Feedback: Incorrect. The enhancer is a 200-base-pair region composed of many cis-acting sequence elements, which together are the basis for specific expression in lymphoid cells.
Textbook Reference: Regulation of
Which of the following experimental approaches is least likely to be used in identifying transcription factor binding sites?
a. Electrophoretic-mobility shift assay
b. Northern blotting
c. DNA footprinting
d. Chromatin immunoprecipitation
Correct Answer: b
Your Answer: b
Answer B Feedback: Correct! Northern blots are used to characterize RNA.
Textbook Reference: Regulation of Transcription in Eukaryotes
Which of the following is not part of the transcription complex?
a. TBP
b. TAFs
c. TFIIH
d. RFC
Correct Answer: d
Your Answer: b
Answer B Feedback: Incorrect. TAFs are TBP-associated factors and interact with TBP.
Textbook Reference: Eukaryotic RNA Polymerases and General Transcription Factors `
Which of the following statements about transcription of ribosomal RNA is false?
a. Ribosomal RNA is transcribed by RNA polymerase I.
b. A single pre-RNA gives rise to the 18S, 5.8S, and 28S rRNAs.
c. TBP binds the TATA sequences in the promoter of the ri
Correct Answer: c
Your Answer: d
Answer D Feedback: Incorrect. This is a true statement.
Textbook Reference: Eukaryotic RNA Polymerases and General Transcription Factors
The lac operon in E. coli is regulated by lactose, which
a. activates an activator of transcription.
b. inactivates an activator of transcription.
c. activates a repressor of transcription.
d. inactivates a repressor of transcription.
Correct Answer: d
Your Answer: c
Answer C Feedback: Incorrect. The repressor is already active in the absence of lactose.
Textbook Reference: Transcription in Prokaryotes
Which of the following best describes the ability of an enhancer to mediate transcription from very distant sites?
a. Looping of the DNA can occur, allowing the transcription factor to get into the proximity of the RNA polymerase.
b. When needed, enhancer
Correct Answer: a
Your Answer: a
Answer A Feedback: Correct! This allows for enhancer regulation from sites located literally kilobases away.
Textbook Reference: Regulation of Transcription in Eukaryotes
Which of the following statements about cis-acting elements is true?
a. They are specific DNA sequences that control the transcription of adjacent genes.
b. Various proteins specifically recognize and bind to these cis-acting sequences.
c. They are utiliz
Correct Answer: d
Your Answer: a
Answer A Feedback: Incorrect. This is a true statement, but the other answer choices are true as well.
Textbook Reference: Regulation of Transcription in Eukaryotes
Which of the following is not an example of a transcription factor DNA-binding domain?
a. Helix-turn-helix
b. Acidic
c. Helix-loop-helix
d. Zinc finger
Correct Answer: b
Your Answer: b
Answer B Feedback: Correct! The acidic domain is commonly found in transcription factors but is not a binding domain. Rather, it is an activation or repressing domain.
Textbook Reference: Regulation of Transcription in Euk
Glucose repression (or catabolite repression) is mediated by several positive transcriptional control mechanisms. Which of the following is not one of those mechanisms?
a. Low levels of glucose activate adenylyl cyclase, increasing synthesis of cAMP.
b. c
Correct Answer: c
Your Answer: d
Answer D Feedback: Incorrect. This is a true statement.
Textbook Reference: Transcription in Prokaryotes
A mutation in the leucine zipper of a transcription factor would directly prevent
a. binding of the transcription factor to its DNA recognition sequences.
b. interaction with other transcription factors in forming hetero- and homodimers.
c. binding of zin
Correct Answer: b
Your Answer: b
Answer B Feedback: Correct! The leucine zipper is a heptad repeat of leucines that are involved directly in interactions with other proteins that contain leucine zippers.
Textbook Reference: Regulation of Transcription in
Which of the following is not involved in relieving transcriptional repression imposed by chromatin?
a. Histone acetylation
b. HMG-14
c. Gcn5p
d. DNA methylation
Correct Answer: d
Your Answer: a
Answer A Feedback: Incorrect. Histone acetylation reduces the positive charge associated with histones, thus weakening their association with DNA and allowing for greater accessibility to transcription factors.
Textbook Re
In prokaryotes, ? factors are necessary for
a. specific binding to certain promoters.
b. low-affinity binding upstream from promoters.
c. elongation of the RNA strand to its end.
d. All of the above
Correct Answer: a
Your Answer: b
Answer B Feedback: Incorrect. The RNA polymerase core, which lacks the ? subunit, binds with low affinity to DNA.
Textbook Reference: Transcription in Prokaryotes
A yeast mutant shows decreased expression of the 5.8S rRNA, the 5S rRNA, and protein-encoding mRNAs. In which of the following might the mutation lie?
a. TATA-binding protein (TBP)
b. Upstream binding factor (UBF)
c. RNA polymerase III
d. TFIIB
Correct Answer: a
Your Answer: b
Answer B Feedback: Incorrect. UBF is a transcription factor specific for RNA polymerase I, and so only the 5.8S, 18S, and 28S rRNAs would be affected.
Textbook Reference: Eukaryotic RNA Polymerases and General Transcriptio
Which of the following both stabilizes and increases the efficiency of translation of an mRNA?
a. Editing
b. Splicing
c. Addition of a 7-methylguanosine cap
d. Addition of the CCA sequence to the 3? end
Correct Answer: c
Your Answer: b
Answer B Feedback: Incorrect. Splicing is the process whereby introns are removed from the pre-mRNA, leaving the correct mRNA for export into the cytoplasm and, subsequently, translation.
Textbook Reference: RNA Processing
A reporter gene is used to
a. identify regulatory sequences from the upstream regions of other genes.
b. determine if a protein binds to a given sequence element.
c. determine if a gene contains introns.
d. determine the stability of a protein.
Correct Answer: a
Your Answer: c
Answer C Feedback: Incorrect. A reporter gene plays no such role.
Textbook Reference: Regulation of Transcription in Eukaryotes
A ribozyme is defined as an enzyme
a. in which an RNA molecule is responsible for the catalytic activity.
b. that catalyzes the cleavage of RNA.
c. involved in translation.
d. that catalyzes the addition of ribose moieties to RNA.
Correct Answer: a
Your Answer: d
Answer D Feedback: Incorrect. An enzyme that adds ribose moieties to RNA is an RNA polymerase.
Textbook Reference: RNA Processing and Turnover