Chapter 17 From Gene to Protein
16) The ʺuniversalʺ genetic code is now known to have exceptions. Evidence for this could be found if which of the following is true? A) If UGA, usually a stop codon, is found to code for an amino acid such as tryptophan (usually coded for by UGG only). B) If one stop codon, such as UGA, is found to have a different effect on translation than another stop codon, such as UAA. C) If prokaryotic organisms are able to translate a eukaryotic mRNA and produce the same polypeptide. D) If several codons are found to translate to the same amino acid, such as serine. E) If a single mRNA molecule is found to translate to more than one polypeptide when there are two or more AUG sites
Answer: A
21) Which of the following mechanisms is (are) used to coordinately control the expression of multiple, related genes in eukaryotic cells? A) organization of the genes into clusters, with local chromatin structures influencing the expression of all the genes at once B) each of the genes sharing a common control element, allowing several activators to turn on their transcription, regardless of their location in the genome C) organizing the genes into large operons, allowing them to be transcribed as a single unit D) a single repressor able to turn off several related genes E) environmental signals that enter the cell and bind directly to their promoters
Answer: A
27) The TATA sequence is found only several nucleotides away from the start site of transcription. This most probably relates to which of the following? A) the number of hydrogen bonds between A and T in DNA B) the triplet nature of the codon C) the ability of this sequence to bind to the start site D) the supercoiling of the DNA near the start site E) the 3-dimensional shape of a DNA molecu
Answer: A
28) A geneticist introduces a transgene into yeast cells and isolates five independent cell lines in which the transgene has integrated into the yeast genome. In four of the lines, the transgene is expressed strongly, but in the fifth there is no expression at all. Which is a likely explanation for the lack of transgene expression in the fifth cell line? A) A transgene integrated into a heterochromatic region of the genome. B) A transgene integrated into a euchromatic region of the genome. C) The transgene was mutated during the process of integration into the host cell genome. D) The host cell lacks the enzymes necessary to express the transgene. E) A transgene integrated into a region of the genome characterized by high histone acetylation.
Answer: A
33) Introns are significant to biological evolution because A) their presence allows exons to be shuffled. B) they protect the mRNA from degeneration. C) they are translated into essential amino acids. D) they maintain the genetic code by preventing incorrect DNA base pairings. E) they correct enzymatic alterations of DNA bases.
Answer: A
37) 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? A) increased chromatin condensation B) decreased chromatin concentration C) abnormalities of mouse embryos D) decreased binding of transcription factors E) inactivation of the selected genes
Answer: A
43) Which of the following is most likely to have a small protein called ubiquitin attached to it? A) a cyclin that usually acts in G1, now that the cell is in G2 B) a cell surface protein that requires transport from the ER C) an mRNA that is leaving the nucleus to be translated D) a regulatory protein that requires sugar residues to be attached E) an mRNA produced by an egg cell that will be retained until after fertilization
Answer: A
44) The phenomenon in which RNA molecules in a cell are destroyed if they have a sequence complementary to an introduced double-stranded RNA is called A) RNA interference. B) RNA obstruction. C) RNA blocking. D) RNA targeting. E) RNA disposal.
Answer: A
70) Sickle-cell disease is probably the result of which kind of mutation? A) point B) frameshift C) nonsense D) nondisjunction E) both B and D
Answer: A
72) Which of the following DNA mutations is the most likely to be damaging to the protein it specifies? A) a base-pair deletion B) a codon substitution C) a substitution in the last base of a codon D) a codon deletion E) a point mutation
Answer: A
80) Which of the following statements describes proto-oncogenes? A) They can code for proteins associated with cell growth. B) They are introduced to a cell initially by retroviruses. C) They are produced by somatic mutations induced by carcinogenic substances. D) Their normal function is to suppress tumor growth E) They are underexpressed in cancer cells
Answer: A
89) If there are two children born from the same parents, and child one inherits a predisposition to retinoblastoma (one of the mutations) and child two does not, but both children develop the retinoblastoma, which of the following would you expect? A) an earlier age of onset in child one B) a history of exposure to mutagens in child one but not in child two C) a more severe cancer in child one D) increased levels of apoptosis in both children E) decreased levels of DNA repair in child one
Answer: A
10) Transcription of the structural genes in an inducible operon A) occurs continuously in the cell. B) starts when the pathwayʹs substrate is present. C) starts when the pathwayʹs product is present. D) stops when the pathwayʹs product is present. E) does not result in the production of enzymes.
Answer: B
20) Which of the following statements best describes the termination of transcription in prokaryotes? A) RNA polymerase transcribes through the polyadenylation signal, causing proteins to associate with the transcript and cut it free from the polymerase. B) RNA polymerase transcribes through the terminator sequence, causing the polymerase to fall off the DNA and release the transcript. C) RNA polymerase transcribes through an intron, and the snRNPs cause the polymerase to let go of the transcript. D) Once transcription has initiated, RNA polymerase transcribes until it reaches the end of the chromosome. E) RNA polymerase transcribes through a stop codon, causing the polymerase to stop advancing through the gene and release the mRNA.
Answer: B
36) 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 using this procedure in Drosophila, she was readily successful in increasing phosphorylation of amino acids adjacent to methylated amino acids in histone tails. Which of the following results would she most likely see? A) increased chromatin condensation B) decreased chromatin concentration C) abnormalities of mouse embryos D) decreased binding of transcription factors E) inactivation of the selected genes
Answer: B
37) Alternative RNA splicing A) is a mechanism for increasing the rate of transcription. B) can allow the production of proteins of different sizes from a single mRNA. C) can allow the production of similar proteins from different RNAs. D) increases the rate of transcription. E) is due to the presence or absence of particular snRNPs.
Answer: B
65) The MyoD protein A) can promote muscle development in all cell types. B) is a transcription factor that binds to and activates the transcription of muscle-related genes. C) was used by researchers to convert differentiated muscle cells into liver cells. D) magnifies the effects of other muscle proteins. E) is a target for other proteins that bind to it.
Answer: B
66) Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on the polypeptide product? A) a deletion of a codon B) a deletion of 2 nucleotides C) a substitution of the third nucleotide in an ACC codon D) a substitution of the first nucleotide of a GGG codon E) an insertion of a codon
Answer: B
7) When this is taken up by the cell, it binds to the repressor so that the repressor no longer binds to the operator: A) operon B) inducer C) promoter D) repressor E) corepressor
Answer: B
71) If a Drosophila female has a homozygous mutation for a maternal effect gene, A) she will not develop past the early embryonic stage. B) all of her offspring will show the mutant phenotype, regardless of their genotype. C) only her male offspring will show the mutant phenotype. D) her offspring will show the mutant phenotype only if they are also homozygous for the mutation. E) only her female offspring will show the mutant phenotype.
Answer: B
73) Which point mutation would be most likely to have a catastrophic effect on the functioning of a protein? A) a base substitution B) a base deletion near the start of a gene C) a base deletion near the end of the coding sequence, but not in the terminator codon D) deletion of three bases near the start of the coding sequence, but not in the initiator codon E) a base insertion near the end of the coding sequence, but not in the terminator codon
Answer: B
77) The product of the bicoid gene in Drosophila could be considered a(n) A) tissue-specific protein. B) cytoplasmic determinant. C) maternal effect. D) inductive signal. E) fertilization product.
Answer: B
15) The genetic code is essentially the same for all organisms. From this, one can logically assume all of the following except A) a gene from an organism could theoretically be expressed by any other organism. B) all organisms have a common ancestor. C) DNA was the first genetic material. D) the same codons in different organisms usually translate into the same amino acids. E) different organisms have the same number of different types of amino acids.
Answer: C
18) Which of the following is true for both prokaryotic and eukaryotic gene expression? A) After transcription, a 3ʹ poly-A tail and a 5ʹ cap are added to mRNA. B) Translation of mRNA can begin before transcription is complete. C) RNA polymerase binds to the promoter region to begin transcription. D) mRNA is synthesized in the 3ʹ → 5ʹ direction. E) The mRNA transcript is the exact complement of the gene from which it was copied.
Answer: C
2) 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) have turned off or slowed down the process of transcription. D) be very actively transcribed and translated. E) induce protein synthesis by not allowing repressors to bind to it.
Answer: C
26) A part of the promoter, called the TATA box, is said to be highly conserved in evolution. Which might this illustrate? A) The sequence evolves very rapidly. B) The sequence does not mutate. C) Any mutation in the sequence is selected against. D) The sequence is found in many but not all promoters. E) The sequence is transcribed at the start of every gene.
Answer: C
32) This binds to a site in the DNA far from the promoter to stimulate transcription: A) enhancer B) promoter C) activator D) repressor E) terminator
Answer: C
35) Which of the following is (are) true of snRNPs? A) They are made up of both DNA and RNA. B) They bind to splice sites at each end of the exon. C) They join together to form a large structure called the spliceosome. D) They act only in the cytosol. E) They attach introns to exons in the correct order
Answer: C
36) During splicing, which molecular component of the spliceosome catalyzes the excision reaction? A) protein B) DNA C) RNA D) lipid E) sugar
Answer: C
39) A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture. She tried decreasing the amount of methylation enzymes in the embryonic stem cells and then allowed the cells to further differentiate. Which of the following results would she most likely see? A) increased chromatin condensation B) decreased chromatin concentration C) abnormalities of mouse embryos D) decreased binding of transcription factors E) inactivation of the selected genes
Answer: C
4) If A, B, and C are all required for growth, a strain that is mutant for the gene encoding enzyme A would be able to grow on which of the following media? A) minimal medium B) minimal medium supplemented with nutrient ʺAʺ only C) minimal medium supplemented with nutrient ʺBʺ only D) minimal medium supplemented with nutrient ʺCʺ only E) minimal medium supplemented with nutrients ʺAʺ and ʺCʺ
Answer: C
41) Gene expression might be altered at the level of post-transcriptional processing in eukaryotes rather than prokaryotes because of which of the following? A) Eukaryotic mRNAs get 5ʹ caps and 3ʹ tails. B) Prokaryotic genes are expressed as mRNA, which is more stable in the cell. C) Eukaryotic exons may be spliced in alternative patterns. D) Prokaryotes use ribosomes of different structure and size. E) Eukaryotic coded polypeptides often require cleaving of signal sequences before localization.
Answer: C
49) In a series of experiments, the enzyme Dicer has been inactivated in cells from various vertebrates, and the centromere is abnormally formed from chromatin. Which of the following is most likely to occur? A) The usual mRNAs transcribed from centromeric DNA will be missing from the cells. B) Tetrads will no longer be able to form during meiosis I. C) Centromeres will be euchromatic rather than heterochromatic and the cells will soon die in culture. D) The cells will no longer be able to resist bacterial contamination. E) The DNA of the centromeres will no longer be able to replicate.
Answer: C
49) What is the most abundant type of RNA? A) mRNA B) tRNA C) rRNA D) pre-mRNA E) hnRNA
Answer: C
58) A cell that remains entirely flexible in its developmental possibilities is said to be A) differentiated. B) determined. C) totipotent. D) genomically equivalent. E) epigenetic.
Answer: C
17) Which of the following nucleotide triplets best represents a codon? A) a triplet separated spatially from other triplets B) a triplet that has no corresponding amino acid C) a triplet at the opposite end of tRNA from the attachment site of the amino acid D) a triplet in the same reading frame as an upstream AUG E) a sequence in tRNA at the 3ʹ end
Answer: D
19) In which of the following actions does RNA polymerase differ from DNA polymerase? A) RNA polymerase uses RNA as a template, and DNA polymerase uses a DNA template. B) RNA polymerase binds to single-stranded DNA, and DNA polymerase binds to double-stranded DNA. C) RNA polymerase is much more accurate than DNA polymerase. D) RNA polymerase can initiate RNA synthesis, but DNA polymerase requires a primer to initiate DNA synthesis. E) RNA polymerase does not need to separate the two strands of DNA in order to synthesize an RNA copy, whereas DNA polymerase must unwind the double helix before it can replicate the DNA.
Answer: D
2) Which of the following is not true of a codon? A) It consists of three nucleotides. B) It may code for the same amino acid as another codon. C) It never codes for more than one amino acid. D) It extends from one end of a tRNA molecule. E) It is the basic unit of the genetic code.
Answer: D
23) Genomic imprinting, DNA methylation, and histone acetylation are all examples of A) genetic mutation. B) chromosomal rearrangements. C) karyotypes. D) epigenetic phenomena. E) translocation.
Answer: D
40) Transcription factors in eukaryotes usually have DNA binding domains as well as other domains also specific for binding. In general, which of the following would you expect many of them to be able to bind? A) repressors B) ATP C) protein-based hormones D) other transcription factors E) tRNA
Answer: D
5) If A, B, and C are all required for growth, a strain mutant for the gene encoding enzyme B would be capable of growing on which of the following media? A) minimal medium B) minimal medium supplemented with ʺAʺ only C) minimal medium supplemented with ʺBʺ only D) minimal medium supplemented with ʺCʺ only E) minimal medium supplemented with nutrients ʺAʺ and ʺBʺ
Answer: D
54) Which of the following is a function of a signal peptide? A) to direct an mRNA molecule into the cisternal space of the ER B) to bind RNA polymerase to DNA and initiate transcription C) to terminate translation of the messenger RNA D) to translocate polypeptides across the ER membrane E) to signal the initiation of transcription
Answer: D
61) Which component of the complex described enters the exit tunnel through the large subunit of the ribosome? A) tRNA with attached lysine (#1) B) tRNA with polypeptide (#2) C) tRNA that no longer has attached amino acid D) newly formed polypeptide E) initiation and elongation factors
Answer: D
64) Why might a point mutation in DNA make a difference in the level of proteinʹs activity? A) It might result in a chromosomal translocation. B) It might exchange one stop codon for another stop codon. C) It might exchange one serine codon for a different serine codon. D) It might substitute an amino acid in the active site. E) It might substitute the N terminus of the polypeptide for the C terminus.
Answer: D
18) If she moves the repressor gene (lac I), along with its promoter, to a position at some several thousand base pairs away from its normal position, which will you expect to occur? A) The repressor will no longer be made. B) The repressor will no longer bind to the operator. C) The repressor will no longer bind to the inducer. D) The lac operon will be expressed continuously. E) The lac operon will function normally.
Answer: E
19) If glucose is available in the environment of E. coli, the cell responds with very low concentration of cAMP. When the cAMP increases in concentration, it binds to CAP. Which of the following would you expect would then be a measurable effect? A) decreased concentration of the lac enzymes B) increased concentration of the trp enzymes C) decreased binding of the RNA polymerase to sugar metabolism-related promoters D) decreased concentration of alternative sugars in the cell E) increased concentrations of sugars such as arabinose in the cell
Answer: E
24) Approximately what proportion of the DNA in the human genome codes for proteins or functional RNA? A) 83% B) 46% C) 32% D) 13% E) 1.5%
Answer: E
38) A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture. One of her colleagues suggested she try increased methylation of C nucleotides in a mammalian system. Which of the following results would she most likely see? A) increased chromatin condensation B) decreased chromatin concentration C) abnormalities of mouse embryos D) decreased binding of transcription factors E) inactivation of the selected genes
Answer: E
50) From the following list, which is the first event in translation in eukaryotes? A) elongation of the polypeptide B) base pairing of activated methionine-tRNA to AUG of the messenger RNA C) the larger ribosomal subunit binds to smaller ribosomal subunits D) covalent bonding between the first two amino acids E) the small subunit of the ribosome recognizes and attaches to the 5ʹ cap of mRNA
Answer: E
59) Which enzyme causes a covalent bond to attach lysine to the polypeptide? A) ATPase B) lysine synthetase C) RNA polymerase D) ligase E) peptidyl transferase
Answer: E
6) Which of the following mutations would be most likely to have a harmful effect on an organism? A) a base-pair substitution B) a deletion of three nucleotides near the middle of a gene C) a single nucleotide deletion in the middle of an intron D) a single nucleotide deletion near the end of the coding sequence E) a single nucleotide insertion downstream of, and close to, the start of the coding sequence
Answer: E
68) Your brother has just purchased a new plastic model airplane. He places all the parts on the table in approximately the positions in which they will be located when the model is complete. His actions are analogous to which process in development? A) morphogenesis B) determination C) induction D) differentiation E) pattern formation
Answer: E
85) Forms of the ras protein found in tumors usually cause which of the following? A) DNA replication to stop B) DNA replication to be hyperactive C) cell-to-cell adhesion to be nonfunctional D) cell division to cease E) growth factor signaling to be hyperactive
Answer: E