Chapter 14

Question 1 Which of the following mutations would be most likely to have a harmful effect on an organism a. a single nucleotide insertion downstream of, and close to, the start of the coding sequence b. a single nucleotide deletion near the end of the coding sequence c. a deletion of three nucleotides near the middle of a gene d. a single nucleotide deletion in the middle of an intron e. a nucleotide-pair substitution

a

Question 15 Which of the following statements is true about protein synthesis in prokaryotes a. Extensive RNA processing is required before prokaryotic transcripts can be translated. b. Prokaryotic cells have complicated mechanisms for targeting proteins to the appropriate cellular organelles. c. Translation requires antibiotic activity. d. Translation can begin while transcription is still in progress. e. Unlike eukaryotes, prokaryotes require no initiation or elongation factors.

d

Question 16 Use the representation in Figure 14.3 to answer the following questions. Figure 14.3 In the transcription event of the previous DNA, where would the promoter be located a. at the 3' end of the newly made RNA b. to the left of the sense strand c. to the left of the template strand d. to the right of the template strand e. to the right of the sense strand

d

Question 10 Use the following information to answer the next few questions. A transfer RNA (#1) attached to the amino acid lysine enters the ribosome. The lysine binds to the growing polypeptide on the other tRNA (#2) already in the ribosome. Where does tRNA #2 move to after this bonding of lysine to the polypeptide a. directly to the cytosol b. P site c. exit tunnel d. A site e. E site

e

Question 27 During splicing, which molecular component of the spliceosome catalyzes the excision reaction a. DNA b. sugar c. lipid d. protein e. RNA

e

Question 11 Transcription in eukaryotes requires which of the following in addition to RNA polymerase a. several transcription factors b. ribosomes and tRNA c. start and stop codons d. the protein product of the promoter e. aminoacyl-tRNA synthetase

a

Question 14 A mutant bacterial cell has a defective aminoacyl-tRNA synthetase that attaches a lysine to tRNAs with the anticodon AAA instead of the normal phenylalanine. The consequence of this for the cell will be that a. proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU. b. the ribosome will skip a codon every time a UUU is encountered. c. the cell will compensate for the defect by attaching phenylalanine to tRNAs with lysine-specifying anticodons. d. none of the options will occur; the cell will recognize the error and destroy the tRNA. e. none of the proteins in the cell will contain phenylalanine.

a

Question 28 Garrod hypothesized that "inborn errors of metabolism" such as alkaptonuria occur because a. genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes. b. enzymes are made of DNA, and affected individuals lack DNA polymerase. c. certain metabolic reactions are carried out by ribozymes, and affected individuals lack key splicing factors. d. many metabolic enzymes use DNA as a cofactor, and affected individuals have mutations that prevent their enzymes from interacting efficiently with DNA. e. metabolic enzymes require vitamin cofactors, and affected individuals have significant nutritional deficiencies.

a

Question 29 Which of the following best describes the significance of the TATA box in eukaryotic promoters a. It is the recognition site for a specific transcription factor. b. It sets the reading frame of the mRNA. c. It prevents supercoiling of the DNA near the start site. d. Its significance has not yet been determined. e. It is the recognition site for ribosomal binding.

a

Question 31 Why might a point mutation in DNA make a difference in the level of a protein's activity a. It might substitute a different amino acid in the active site. b. It might exchange one serine codon for a different serine codon. c. It might result in a chromosomal translocation. d. It might substitute the N-terminus of the polypeptide for the C-terminus. e. It might exchange one stop codon for another stop codon.

a

Question 33 If a newly made polypeptide is to be secreted from a cell, what must occur before it is secreted a. Its signal sequence must target it to the ER, after which it goes to the Golgi. b. Its signal sequence must cause it to be encased in a vesicle as soon as it is translated. c. Its signal sequence must target it to the plasma membrane, where it causes exocytosis. d. Its signal sequence must be cleaved off before the polypeptide can enter the ER. e. It must be translated by a ribosome that remains free of attachment to the ER.

a

Question 40 Which of the following experimental procedures is most likely to hasten mRNA degradation in a eukaryotic cell a. removal of the 5' cap b. enzymatic lengthening of the poly-A tail c. methylation of C nucleotides d. removal of one or more exons e. methylation of histones

a

Question 12 The following information should be used for the next few questions. A part of an mRNA molecule with the following sequence is being read by a ribosome: 5' CCG-ACG 3' (mRNA). The charged transfer RNA molecules shown in Figure 14.4 (with their anticodons shown in the 3' to 5' direction) are available. Two of them can correctly match the mRNA so that a dipeptide can form. Figure 14.4 The anticodon loop of the first tRNA that will complement this mRNA is a. 5' UGC 3'. b. 3' GGC 5'. c. 5' ACG 3'. d. 5' GGC 3'. e. 3' UGC 5'.

b

Question 17 Figure 14.5 Figure 14.5 represents tRNA that recognizes and binds a particular amino acid (in this instance, phenylalanine). Which codon on the mRNA strand codes for this amino acid a. CAU b. UUC c. GUA d. GUG e. UGG

b

Question 22 A frameshift mutation could result from a. deletion of three consecutive bases. b. either an insertion or a deletion of a base. c. a base insertion only. d. a base substitution only. e. a base deletion only.

b

Question 25 The most commonly occurring mutation in people with cystic fibrosis is a deletion of a single codon. This results in a. a frameshift mutation. b. a polypeptide missing an amino acid. c. a nucleotide mismatch. d. a base-pair substitution. e. a nonsense mutation.

b

Question 3 An experimenter has altered the 3' end of the tRNA corresponding to the amino acid methionine in such a way as to remove the 3' AC. Which of the following hypotheses describes the most likely result a. The anticodon will not bind with the mRNA codon. b. The amino acid methionine will not become covalently bound. c. tRNA will not form a cloverleaf. d. The nearby stem end will pair improperly. e. The aminoacyl-tRNA synthetase will not be formed.

b

Question 30 Suppose that an error in transcription alters the formation of a single tRNA molecule in a cell. The altered tRNA still attaches to the same amino acid (Phe), but its anticodon loop has the sequence AAU, which binds to the mRNA codon UUA (usually specifying leucine, Leu). What will be the effect on translation in this cell a. The tRNA-Leu will not be able to enter the ribosome to bind to the UUA codon. b. One altered tRNA molecule will be relatively inconsequential because it will compete with many "normal" ones. c. The altered tRNA will cause this mRNA to make only nonfunctioning product. d. The altered tRNA will be so unstable that it will not participate in translation. e. The altered tRNA will result in an amino acid variant in all copies of the protein.

b

Question 34 A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is a. AAA. b. UUU. c. UUA. d. TTT. e. either UAA or TAA, depending on first base wobble.

b

Question 38 Which of the following is not true of RNA processing a. A primary transcript is often much longer than the final RNA molecule that leaves the nucleus. b. Exons are cut out before mRNA leaves the nucleus. c. RNA splicing can be catalyzed by spliceosomes. d. Ribozymes may function in RNA splicing. e. Nucleotides may be added at both ends of the RNA.

b

Question 42 The "universal" genetic code is now known to have exceptions. Evidence for this can be found if which of the following is true a. If a single mRNA molecule is found to translate to more than one polypeptide when there are two or more AUG sites. b. If UGA, usually a stop codon, is found to code for an amino acid such as tryptophan (usually coded for by UGG only). c. If one stop codon, such as UGA, is found to have a different effect on translation than another stop codon, such as UAA. d. If several codons are found to translate to the same amino acid, such as serine. e. If prokaryotic organisms are able to translate a eukaryotic mRNA and produce the same polypeptide

b

Question 9 Which of the following statements best describes the termination of transcription in prokaryotes a. Once transcription has initiated, RNA polymerase transcribes until it reaches the end of the chromosome. b. RNA polymerase transcribes through the terminator sequence, causing the polymerase to separate from the DNA and release the transcript. c. RNA polymerase transcribes through a stop codon, causing the polymerase to stop advancing through the gene and release the mRNA. d. RNA polymerase transcribes through an intron, and the snRNPs cause the polymerase to let go of the transcript. e. RNA polymerase transcribes through the polyadenylation signal, causing proteins to associate with the transcript and cut it free from the polymerase.

b

Question 21 Which of the following is a function of a poly-A signal sequence a. It allows the 3' end of the mRNA to attach to the ribosome. b. It is a sequence that codes for the hydrolysis of the RNA polymerase. c. It codes for a sequence in eukaryotic transcripts that signals enzymatic cleavage ~10—35 nucleotides away. d. It adds the poly-A tail to the 3' end of the mRNA. e. It adds a 7-methylguanosine cap to the 3' end of the mRNA.

c

Question 24 Garrod's information about the enzyme alteration resulting in alkaptonuria led to further elucidation of the same pathway in humans. Phenylketonuria (PKU) occurs when another enzyme in the pathway is altered or missing, resulting in a failure of phenylalanine (phe) to be metabolized to another amino acid: tyrosine. Tyrosine is an earlier substrate in the pathway altered in alkaptonuria. How might PKU affect the presence or absence of alkaptonuria a. Anyone with PKU has mild symptoms of alkaptonuria. b. Anyone with PKU must also have alkaptonuria. c. It would have no effect, because tyrosine is also available from the diet. d. It would have no effect, because PKU occurs several steps away in the pathway. e. Anyone with PKU is born with a predisposition to later alkaptonuria.

c

Question 36 In the 1920s, Muller discovered that X-rays caused mutation in Drosophila. In a related series of experiments in the 1940s, Charlotte Auerbach discovered that chemicals—she used nitrogen mustards—have a similar effect. A new chemical food additive is developed by a cereal manufacturer. Why do we test for its ability to induce mutation a. We want to be sure that it increases the rate of mutation sufficiently. b. We worry that it might cause mutation in cereal grain plants. c. We want to prevent any increase in mutation frequency. d. We want to make sure that it does not emit radiation. e. We worry about its ability to cause infection.

c

Question 37 Use the following model of a eukaryotic transcript to answer the next few questions. 5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3' Which components of the previous molecule will also be found in mRNA in the cytosol a. 5' E1 I1 E2 I2 E3 I3 E4 3' b. 5' UTR I1 I2 I3 UTR 3' c. 5' UTR E1 E2 E3 E4 UTR 3' d. 5' E1 E2 E3 E4 3' e. 5' I1 I2 I3 3'

c

Question 39 The following questions refer to the simple metabolic pathway in Figure 14.1. Figure 14.1 According to Beadle and Tatum's hypothesis, how many genes are necessary for this pathway a. 1 b. 0 c. 2 d. 3 e. It cannot be determined from the pathway

c

Question 45 Use the following information to answer the next few questions. The enzyme polynucleotide phosphorylase randomly assembles nucleotides into a polynucleotide polymer. You add polynucleotide phosphorylase to a solution of ATP, GTP, and UTP. How many artificial mRNA 3 nucleotide codons would be possible a. 9 b. 3 c. 27 d. 6 e. 81

c

Question 5 Which of the following is the first event to take place in translation in eukaryotes a. base pairing of activated methionine-tRNA to AUG of the messenger RNA b. binding of the larger ribosomal subunit to smaller ribosomal subunits c. the small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA d. covalent bonding between the first two amino acids e. elongation of the polypeptide

c

Question 8 Which of the following does not occur in prokaryotic gene expression, but does occur in eukaryotic gene expression a. mRNA, tRNA, and rRNA are transcribed. b. Transcription can begin as soon as translation has begun even a little. c. A poly-A tail is added to the 3' end of an mRNA and a cap is added to the 5' end. d. RNA polymerase binds to the promoter. e. RNA polymerase requires a primer to elongate the molecule.

c

Question 19 The following questions refer to the table of codons in Figure 14.2. Figure 14.2 A peptide has the sequence NH2-phe-pro-lys-gly-phe-pro-COOH. Which of the following sequences in the coding strand of the DNA could code for this peptide a. 3' AUG-AAA-GGG-TTT-CCC-AAA-GGG b. 5' ACT-TAC-CAT-AAA-CAT-TAC-UGA c. 5' GGG-AAA-TTT-AAA-CCC-ACT-GGG d. 5' TTT-CCC-AAA-GGG-TTT-CCC e. 3' UUU-CCC-AAA-GGG-UUU-CCC

d

Question 2 Which small-scale mutation would be most likely to have a catastrophic effect on the functioning of a protein a. a base deletion near the end of the coding sequence, but not in the terminator codon b. deletion of three bases near the start of the coding sequence, but not in the initiator codon c. a base substitution d. a base deletion near the start of a gene e. a base insertion near the end of the coding sequence, but not in the terminator codon

d

Question 23 Which of the following is not true of a codon a. It is the basic unit of the genetic code. 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 consists of three nucleotides.

d

Question 26 Figure 14.5 The tRNA shown in Figure 14.5 has its 3' end projecting beyond its 5' end. What will occur at this 3' end a. The small and large subunits of the ribosome will attach to it. b. The codon and anticodon complement one another. c. The excess nucleotides (ACCA) will be cleaved off at the ribosome. d. The amino acid binds covalently. e. The 5' cap of the mRNA will become covalently bound.

d

Question 35 Using the following figure, identify a 5' → 3' sequence of nucleotides in the DNA template strand for an mRNA coding for the polypeptide sequence Phe-Pro-Lys. a. 5´-AAACCCUUU-3' b. 5´-GAACCCCTT-3' c. 5´-AAAACCTTT-3' d. 5´-CTTCGGGAA-3' e. 5´-UUUGGGAAA-3'

d

Question 41 When the genome of a particular species is said to include 20,000 protein-coding regions, what does this imply a. Each gene codes for one protein. b. The species is highly evolved. c. Any other regions are "junk" DNA. d. There are also genes for RNAs other than mRNA. e. There are 20,000 genes.

d

Question 6 In comparing DNA replication with RNA transcription in the same cell, which of the following is true only of replication a. It uses RNA polymerase. b. The process occurs in the nucleus of a eukaryotic cell. c. It makes a new molecule from its 5' end to its 3' end. d. The entire template molecule is represented in the product. e. The process is extremely fast once it is initiated.

d

Question 13 Use the following information to answer the next few questions. A transfer RNA (#1) attached to the amino acid lysine enters the ribosome. The lysine binds to the growing polypeptide on the other tRNA (#2) already in the ribosome. Which component of the complex described enters the exit tunnel through the large subunit of the ribosome a. tRNA with polypeptide (#2) b. initiation and elongation factors c. tRNA that no longer has attached amino acid d. tRNA with attached lysine (#1) e. newly formed polypeptide

e

Question 18 Gene expression in the domain Archaea in part resembles that of bacteria and in part that of the domain Eukarya. In which way is it most like the domain Eukarya a. Initiation of translation is like that of domain Eukarya. b. There is only one RNA polymerase. c. Post-transcriptional splicing is like that of Eukarya. d. Transcription termination often involves attenuation. e. Domain Archaea has numerous transcription factors.

e

Question 20 In an experimental situation, a student researcher inserts an mRNA molecule into a eukaryotic cell after he has removed its 5' cap and poly-A tail. Which of the following would you expect him to find a. The molecule is digested by restriction enzymes in the nucleus. b. The molecule attaches to a ribosome and is translated, but more slowly. c. The cell recognizes the absence of the tail and polyadenylates the mRNA. d. The mRNA could not exit the nucleus to be translated. e. The molecule is digested by exonucleases because it is no longer protected at the 5' end.

e

Question 32 Which of the following mutations is most likely to cause a phenotypic change a. a nucleotide substitution in an exon coding for a transmembrane domain b. a duplication of all or most introns c. a large inversion whose ends are each in the same region between genes d. a frameshift mutation one codon away from the 3' end of the nontemplate strand e. a single nucleotide deletion in an exon coding for an active site

e

Question 4 Which component is not directly involved in translation a. mRNA b. ribosomes c. GTP d. tRNA e. DNA

e

Question 43 In eukaryotic cells, transcription cannot begin until a. the 5' caps are removed from the mRNA. b. the DNA introns are removed from the template. c. DNA nucleases have isolated the transcription unit. d. the two DNA strands have completely separated and exposed the promoter. e. several transcription factors have bound to the promoter.

e

Question 44 The following questions refer to the table of codons in Figure 14.2. Figure 14.2 What amino acid sequence will be generated, based on the following mRNA codon sequence 5' AUG-UCU-UCG-UUA-UCC-UUG 3' a. met-ser-leu-ser-leu-ser b. met-leu-phe-arg-glu-glu c. met-arg-glu-arg-glu-arg d. met-glu-arg-arg-glu-leu e. met-ser-ser-leu-ser-leu

e

Question 7 Use the following model of a eukaryotic transcript to answer the next few questions. 5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3' When the spliceosome binds to elements of this structure, where can it attach a. to an adjacent intron and exon b. to the exons c. to the 5' UTR d. to the 3' UTR e. to the end of an intron

e