Chapter 17
If a bacteria contained a mutant aminoacyl-tRNA synthetase that attaches a lysine instead of the normal phenylalanine to tRNAs with the anticodon AAA which of the following would occur? A) Proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU. B) None of the proteins in the cell will contain phenylalanine. C) The cell will compensate for the defect by attaching phenylalanine to tRNAs with lysine-specifying anticodons. D) The ribosome will skip a codon every time a UUU is encountered.
A
RNA is single stranded, can hydrogen-bond with other nucleic acids, and has functional groups that can function in catalysis. These characteristics support that RNA could have which of the following cellular roles? A) forming peptide bond B) stagging proteins for degradation by lysosomes C) targeting proteins for secretion D) forming scaffolds for ribosome attachment
A
Transcription in eukaryotes requires which of the following molecules in addition to RNA polymerase? A) transcription factors B) aminoacyl-tRNA synthetase C) ribosomes and tRNA D) anticodons
A
Translation termination occurs when a ribosome interacts with which of the following structures? A) a stop codon B) the poly-A tail C) the end of the mRNA molecule. D) the 5' cap
A
Using the CRISPR-Cas9 system to correct a genetic defect in a mouse brings with it which of the following risks? A) altering non-target mouse genes needed for cell function B) introducing CRISPR-Cas9 gene into the animal's genome C) increasing the animal's susceptibility to bacteriophage infection D) decreasing the animal's ability to repair other mutations
A
Which of the following molecules carries information from DNA and directs incorporation of amino acids at the ribosome? A) mRNA B) rRNA C) tRNA D) enzymes
A
Which of the following processes occurs in prokaryotes but not in eukaryotes? A) simultaneous transcription and translation of the same mRNA B) translocation into the ER C) removing introns from pre-RNA D) translation in the absence of a ribosome
A
Which of the following statements best describes the termination of transcription in prokaryotes? A) RNA polymerase transcribes through the terminator sequence, causing the polymerase to separate from the DNA and release the transcript. B) Once transcription has initiated, RNA polymerase transcribes until it reaches the end of the chromosome and releases. C) RNA polymerase transcribes through the polyadenylation signal, causing proteins to associate with the transcript and cut it free from the polymerase. D) RNA polymerase transcribes through a stop codon, causing the polymerase to stop advancing through the gene and release the mRNA.
A
Which of the following statements best supports the one gene-one enzyme hypothesis? A) Which of the following statements best supports the one gene-one enzyme hypothesis? A mutation in a single gene can result in a defective protein. B) Alkaptonuria results when individuals lack multiple enzymes involved in the catalysis of homogentisic acid. C) Sickle-cell anemia results in normal hemoglobin. D) Multiple antibody genes can code for different related proteins, depending on the splicing that takes place post-transcriptionally.
A
Accuracy in translation of mRNA into the primary structure of a polypeptide depends on specificity in the ________. A) binding of the anticodon to small subunit of the ribosome B) attachment of amino acids to tRNAs C) attachment of amino acid's carboxyl group with the amine of the next amino acid. D) binding of ribosomes to the mRNA
B
In eukaryotes which of the following is the first step in translation? A) the ribosome reaches a stop codon B) the small subunit of the ribosome recognizes and attaches near the 5' cap of mRNA C) base pairing of activated methionine-tRNA to AUG of the messenger RNA D) binding of the larger ribosomal subunit to smaller ribosomal subunits
B
Rank the following mutations with respect to their likelihood of affecting the structure of the polypeptide (from most likely to affect structure to least likely). 1. insertion mutation in the middle of an intron 2. deletion of 3 bases crossing an intron-exon border 3. substitution mutation at the third position of a codon 4. substitution mutation at the second position of a codon A)4, 3, 2, 1 B) 2, 3, 4, 1 C) 1, 2, 4, 3 D) 3, 4, 2, 1
B
The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following statements to be true? A) Different organisms have different types of amino acids. B) A gene from an organism can theoretically be expressed by any other organism. C) DNA was the first genetic material. D) The same codons in different organisms translate into different amino acids.
B
What is the function of the release factor during translation in eukaryotes? A) It supplies a source of energy for termination of translation. B) It binds to the stop codon in the A site in place of a tRNA. C) It releases the amino acid from its tRNA to allow the amino acid to form a peptide bond. D) It releases the ribosome from the ER to allow polypeptides into the cytosol.
B
Which answer correctly compares the primary transcript in a prokaryotic cell with the functional mRNA? A) the primary transcript and the mRNA both contain introns B) the primary transcript is the same size as the mRNA C) the primary transcript is smaller than the mRNA D) the primary transcript is larger than the mRNA
B
Which of the following best explains the observation that in bacteria, there are 61 mRNA codons that specify an amino acid, but only 45 tRNAs? A) The DNA codes 61 tRNAs, but some are destroyed after transcription. B) The rules for base pairing between the third base of a codon and tRNA are flexible. C) Many codons are never used, so the tRNAs that recognize them are dispensable. D) Some tRNAs have anticodons that recognize four or more different codons.
B
Which of the following changes in an exon is most likely to result in a nonfunctional protein product? A) a codon deletion B) a base-pair deletion C) a substitution in the last base of a codon D) an addition of three nucleotides
B
Which of the following characteristics of gene expression is shared by eukaryotic and prokaryotic cells? A) Ribosomes attach to the plasma membrane when producing secreted proteins. B) Signal sequences are needed for the production of membrane proteins. C) Translation occurs before transcription. D) Transcription of an mRNA is temporally separated from its translation.
B
Which of the following processes occurs as part of transcription? A) DNA is replicated B) RNA is synthesized C) mRNA attaches to ribosomes D) proteins are synthesized
B
Which of the following processes will occur at the exposed 3' end of a tRNA molecule? A) The 5' cap of the mRNA will bind covalently. B) An amino acid will bind covalently. C) The single stranded nucleotides (ACCA) will be removed to stabilize the tRNA. D) The small and large subunits of the ribosome will attach to the 3" end.
B
Which of the following statements describes the effect of a nonsense mutation on a gene? A) It changes only one amino acid in the encoded protein. B) It introduces a premature stop codon into the mRNA. C) It alters the reading frame of the mRNA. D) It has no effect on the amino acid sequence of the encoded protein.
B
During the elongation phase of translation, which site in the ribosome represents the first location where a codon pairs with an anticodon? A) E site B) P site C) A site D) the large ribosomal subunit
C
Post-translational modifications of proteins may include which of the following processes? A) synthesis of peptide bonds B) addition of a 5' cap C) addition of carbohydrates to form a glycoprotein D) removal of introns
C
Use the scheme to answer the question. I −→−−−−enzymeX→enzymeX II −→−−−−enzymeY→enzymeY III −→−−−−enzymeZ→enzymeZ IV Refer to the metabolic pathway illustrated. If I, II, III, and IV are all required for growth, a bacterial strain that does not make enzyme X would be able to grow on medium supplemented with which of the following nutrient(s)? A) nutrient I only B) nutrient II only C) nutrients I and II only D) nutrients II, III, and IV only
C
Which answer correctly compares the primary transcript in the nucleus of a eukaryotic cell with the functional mRNA? A) the primary transcript is the same size as the mRNA B) both the primary transcript and mRNA contain introns C) the primary transcript is larger than the mRNA D) the primary transcript is smaller than the mRNA
C
Which of the following best describes the redundancy in the genetic code? A) The genetic code is different for different domains of organisms. B) A single codon can specify the addition of more than one amino acid. C) More than one codon can specify the addition of the same amino acid. D) The genetic code is universal (the same for all organisms).
C
Which of the following characteristics is directly related to the coding of a single amino acid during the process of translation? A) the base sequence at the tRNA 5' end B) the amino acetyl tRNA synthase used C) the three-base sequence of mRNA D) the complementary binding of DNA with RNA
C
Which of the following molecular structures contains codons? A) tRNA B) rRNA C) mRNA D) a protein
C
Which of the following statements best describes the significance of the TATA box in the promoters of eukaryotes? A) It sets the reading frame of the mRNA during translation. B) It is the recognition site for ribosomal binding during translation. C) It is the recognition site for the binding of a specific transcription factor. D) It is the recognition site for ribosomal binding during transcription.
C
Which of the following statements correctly describes Archibald Garrod's hypothesis for how "inborn errors of metabolism" such as alkaptonuria occur? A) Enzymes are made of DNA, and affected individuals lack DNA polymerase. B) Metabolic enzymes require vitamin cofactors, and affected individuals have significant nutritional deficiencies. C) Genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes. D) Certain metabolic reactions are carried out by ribozymes, and affected individuals lack key splicing factors.
C
Which of the following statements correctly describes a ribozyme? A) It is an enzyme that synthesizes RNA as part of the transcription process. B) It is an enzyme that catalyzes the association between the large and small ribosomal subunits. C) It is an RNA with catalytic activity. D) It is a catalyst that uses RNA as a substrate.
C
Which of the following statements is true about protein synthesis in prokaryotes? A) Translation requires no initiation or elongation factors. B) Protein targeting to cellular organelles requires recognition of signal sequences. C) Translation can begin while transcription is still in progress. D) Extensive RNA processing is required before transcripts can be translated.
C
Which of the following structures is needed for the translation initiation complex to form in eukaryotes? A) 5' AUG 3' B) promoter5' C) cap D) exon
C
While characterizing an error-prone organism, researchers found that each of the following types of mutations occurred immediately downstream of the translation start site. Which type of mutation is likely to have the most serious effect on the function of the polypeptide product? A) a deletion of a codon B) a substitution of the third nucleotide in an ACC codon C) a deletion of two nucleotides D) a substitution of the first nucleotide of a GGG codoN
C
A particular triplet of bases in the template strand of DNA is 5'-AAA-3'. The anticodon on the tRNA that binds the mRNA codon is ________. A) 5'-UUA-3' B) 3'-UUU-5' C) 5'-TTT-3' D) 3'-AAA-5'
D
A particular triplet of bases in the template strand of DNA is 5'-AGT-3'. What would be the corresponding codon for the mRNA that is transcribed? A) 3'-ACU-5' B) 5'-UCA-3' C) 5'-AGT-3' D) 3'-UCA-5'
D
An mRNA molecule with the sequence 5'-CCG-ACG-3'is being read by a ribosome.During translation which of the following tRNA anticodons will be the first to productively bind with this mRNA? A) 5'-UGC-3' B) 5'-GGC-3' C) 3'-UGC-5' D) 3'-GGC-5'
D
In eukaryotes, there are several different types of RNA polymerase. Which type is involved in transcription of mRNA for a protein? A) primase B) RNA polymerase I C) RNA polymerase III D) RNA polymerase II
D
Two mRNAs (mRNA X and mRNA Y) are synthesized with the same exon sequences but poly-A tails of very different lengths. mRNA X is 7,500 bases long. mRNA Y is 6,900 bases long. The mRNA's are added to separate in vitro translation mixtures containing radioactive methionine and the reactions are allowed to proceed for 30 minutes. When the mixtures are analyzed which of the following outcomes will most likely occur? A) The mRNA X mixture will contain radioactive proteins but the mRNA Y mixture will not. B) The radioactive proteins in the mRNA X mixture will be larger in size than those in the mRNA Y mixture. C) The radioactive proteins in the mRNA X mixture will begin with methionine while those in the mRNA Y mixture will not. D) The mRNA X mixture will contain more radioactive proteins than the mRNA Y mixture.
D
Which answer correctly compares prokaryotic and eukaryotic codons? A) Prokaryotic codons usually specify different amino acids than those of eukaryotes. B) Prokaryotic codons usually contain different bases than those of eukaryotes. C) Organism within a phylum share codons that are distinct from organisms in other phyla. D) Organisms utilize codons that are nearly universal among all organisms.
D
Which of the following is most likely to occur if a researcher removes the 5' cap and poly-A tail of an mRNA and inserts the mRNA molecule into a eukaryotic cell? A) The cell will add a new poly-A tail to the mRNA. B) The mRNA will attaches to a ribosome and be translated, but more slowly. C) The mRNA will be quickly converted into a ribosomal subunit. D) The molecule will be degraded by enzymes.
D
Which of the following molecules directly participates in the process of translation? A) mRNA, tRNA, and DNA B) mRNA, tRNA, DNA, and rRNA C) mRNA, DNA, and rRNA D) mRNA, tRNA, and rRNA
D
Which of the following processes correctly describes alternative RNA splicing? A) It is a mechanism for increasing the rate of translation. B) It can allow the production of similar proteins from different RNAs. C) It increases the rate of transcription. D) It can allow the production of proteins of different sizes and functions from a single mRNA.
D
Which of the following statements about RNA processing is correct? A) A primary transcript is often much shorter than the final RNA molecule that leaves the nucleus. B) Exons are removed before mRNA leaves the nucleus. C) RNA splicing can be catalyzed by tRNA. D) Ribozymes may function in RNA splicing.
D
Which of the following statements correctly describes the function of a signal peptide? A) It terminates translation of messenger RNA. B) It signals the initiation of transcription. C) It directs an mRNA molecule into the lumen of the ER. D) It helps target a protein to the ER.
D
