Chapter 17 Bio

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) Domain Archaea have numerous transcription factors. B) Initiation of translation is like that of domain Eukarya. C) There is only one RNA polymerase. D) Transcription termination often involves attenuation. E) Post-transcriptional splicing is like that of Eukarya.

A) Domain Archaea have numerous transcription factors.

What is the function of GTP in translation? A) GTP energizes the formation of the initiation complex, using initiation factors. B) GTP hydrolyzes to provide phosphate groups for tRNA binding. C) GTP hydrolyzes to provide energy for making peptide bonds. D) GTP supplies phosphates and energy to make ATP from ADP. E) GTP separates the small and large subunits of the ribosome at the stop codon.

A) GTP energizes the formation of the initiation complex, using initiation factors.

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

A) a base-pair deletion

When the ribosome reaches a stop codon on the mRNA, no corresponding tRNA enters the A site. If the translation reaction were to be experimentally stopped at this point, which of the following would you be able to isolate? A) an assembled ribosome with a polypeptide attached to the tRNA in the P site B) separated ribosomal subunits, a polypeptide, and free tRNA C) an assembled ribosome with a separated polypeptide D) separated ribosomal subunits with a polypeptide attached to the tRNA E) a cell with fewer ribosomes

A) an assembled ribosome with a polypeptide attached to the tRNA in the P site

What is the function of the release factor (RF)? A) It separates tRNA in the A site from the growing polypeptide. 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 supplies a source of energy for termination of translation. E) It releases the ribosome from the ER to allow polypeptides into the cytosol.

B) It binds to the stop codon in the A site in place of a tRNA.

When the function of the newly made polypeptide is to be secreted from the cell where it has been made, what must occur? A) It must be translated by a ribosome that remains free of attachment to the ER. B) Its signal sequence must target it to the ER, from which it goes to the Golgi. C) It has a signal sequence that must be cleaved off before it can enter the ER. D) It has a signal sequence that targets it to the cell's plasma membrane where it causes exocytosis. E) Its signal sequence causes it to be encased in a vesicle as soon as it is translated.

B) Its signal sequence must target it to the ER, from which it goes to the Golgi.

Suppose that an induced mutation removes most of the 5' end of the 5' UTR. What might result? A) Removal of the 5' UTR has no effect because the exons are still maintained. B) Removal of the 5' UTR also removes the 5' cap and the mRNA will quickly degrade. C) The 3' UTR will duplicate and one copy will replace the 5' end. D) The first exon will not be read because I1 will now serve as the UTR. E) Removal of the 5' UTR will result in the strand not binding to tRNAs.

B) Removal of the 5' UTR also removes the 5' cap and the mRNA will quickly degrade.

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) Translation can begin while transcription is still in progress. C) Prokaryotic cells have complicated mechanisms for targeting proteins to the appropriate cellular organelles. D) Translation requires antibiotic activity. E) Unlike eukaryotes, prokaryotes require no initiation or elongation factors.

B) Translation can begin while transcription is still in progress.

Which small-scale 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

B) a base deletion near the start of a gene

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 two 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

B) a deletion of two nucleotides

When translating secretory or membrane proteins, ribosomes are directed to the ER membrane by A) a specific characteristic of the ribosome itself, which distinguishes free ribosomes from bound ribosomes. B) a signal-recognition particle that brings ribosomes to a receptor protein in the ER membrane. C) moving through a specialized channel of the nucleus. D) a chemical signal given off by the ER. E) a signal sequence of RNA that precedes the start codon of the message.

B) a signal-recognition particle that brings ribosomes to a receptor protein in the ER membrane.

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

B) can allow the production of proteins of different sizes from a single mRNA.

The process of translation, whether in prokaryotes or eukaryotes, requires tRNAs, amino acids, ribosomal subunits, and which of the following? A) polypeptide factors plus ATP B) polypeptide factors plus GTP C) polymerases plus GTP D) SRP plus chaperones E) signal peptides plus release factor

B) polypeptide factors plus GTP

A mutant bacterial cell has a defective aminoacyl 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) none of the proteins in the cell will contain phenylalanine. B) proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU. 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. E) none of the options will occur; the cell will recognize the error and destroy the tRNA.

B) proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU.

There are 61 mRNA codons that specify an amino acid, but only 45 tRNAs. This is best explained by the fact that A) some tRNAs have anticodons that recognize four or more different codons. 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) the DNA codes for all 61 tRNAs but some are then destroyed. E) competitive exclusion forces some tRNAs to be destroyed by nucleases.

B) the rules for base pairing between the third base of a codon and tRNA are flexible.

5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3' 24) Which components of the previous molecule will also be found in mRNA in the cytosol? A) 5' UTR I1 I2 I3 UTR 3' B) 5' E1 E2 E3 E4 3' C) 5' UTR E1 E2 E3 E4 UTR 3' D) 5' I1 I2 I3 3' E) 5' E1 I1 E2 I2 E3 I3 E4 3'

C) 5' UTR E1 E2 E3 E4 UTR 3'

If a protein is coded for by a single gene and this protein has six clearly defined domains, which number of exons below is the gene likely to have? A) 1 B) 5 C) 8 D) 12 E) 14

C) 8

What is the effect of a nonsense mutation in a gene? A) It changes an amino acid in the encoded protein. B) It has no effect on the amino acid sequence of the encoded protein. C) It introduces a premature stop codon into the mRNA. D) It alters the reading frame of the mRNA. E) It prevents introns from being excised.

C) It introduces a premature stop codon into the mRNA.

Which of the following is true of transcription in domain Archaea? A) It is regulated in the same way as in domain Bacteria. B) There is only one kind of RNA polymerase. C) It is roughly simultaneous with translation. D) Promoters are identical to those in domain Eukarya. E) It terminates in a manner similar to bacteria.

C) It is roughly simultaneous with translation.

Suppose that a mutation alters the formation of a tRNA such that it still attaches to the same amino acid (phe) but its anticodon loop has the sequence AAU that binds to the mRNA codon UUA (that usually specifies leucine leu). A) The modified tRNA will cause this mRNA to make only nonfunctioning product. B) The tRNA-leu will not be able to enter the site of the ribosome to bind to the UUA. C) One mutated tRNA molecule will be relatively inconsequential because it will compete with many "normal" ones. D) The tRNA will be so unstable that it will not participate in translation. E) The mutated tRNA will result in an amino acid variant in all copies of the protein.

C) One mutated tRNA molecule will be relatively inconsequential because it will compete with many "normal" ones.

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) tRNA will not form a cloverleaf. B) The nearby stem end will pair improperly. C) The amino acid methionine will not bind. D) The anticodon will not bind with the mRNA codon. E) The aminoacylsynthetase will not be formed.

C) The amino acid methionine will not bind.

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) TTT. B) UUA. C) UUU. D) AAA. E) either UAA or TAA, depending on first base wobble.

C) UUU.

Of the following, which is the most current description of a gene? A) a unit of heredity that causes formation of a phenotypic characteristic B) a DNA subunit that codes for a single complete protein C) a DNA sequence that is expressed to form a functional product: either RNA or polypeptide D) a DNA—RNA sequence combination that results in an enzymatic product E) a discrete unit of hereditary information that consists of a sequence of amino acids

C) a DNA sequence that is expressed to form a functional product: either RNA or polypeptide

In order for a eukaryotic gene to be engineered into a bacterial colony to be expressed, what must be included in addition to the coding exons of the gene? A) the introns B) eukaryotic polymerases C) a bacterial promoter sequence D) eukaryotic ribosomal subunits E) eukaryotic tRNAs

C) a bacterial promoter sequence

In the structural organization of many eukaryotic genes, individual exons may be related to which of the following? A) the sequence of the intron that immediately precedes each exon B) the number of polypeptides making up the functional protein C) the various domains of the polypeptide product D) the number of restriction enzyme cutting sites E) the number of start sites for transcription

C) the various domains of the polypeptide product

5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3' Which of the following is a useful feature of introns for this model? A) They are translated into small polypeptides. B) They become parts of snRNPs. C) Each intron has enzymatic properties. D) Introns allow exon shuffling. E) Introns protect exon structure.

D) Introns allow exon shuffling.

Why might a point mutation in DNA make a difference in the level of protein's 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.

D) It might substitute an amino acid in the active site.

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 mRNA could not exit the nucleus to be translated. B) The cell recognizes the absence of the tail and polyadenylates the mRNA. C) The molecule is digested by restriction enzymes in the nucleus. D) The molecule is digested by exonucleases since it is no longer protected at the 5' end. E) The molecule attaches to a ribosome and is translated, but more slowly.

D) The molecule is digested by exonucleases since it is no longer protected at the 5' end.

When the genome of a particular species is said to include 20,000 protein-coding regions, what does this imply? A) There are 20,000 genes. B) Each gene codes for one protein. C) Any other regions are "junk" DNA. D) There are also genes for RNAs other than mRNA. E) The species is highly evolved.

D) There are also genes for RNAs other than mRNA.

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 worry that it might cause mutation in cereal grain plants. B) We want to make sure that it does not emit radiation. C) We want to be sure that it increases the rate of mutation sufficiently. D) We want to prevent any increase in mutation frequency. E) We worry about its ability to cause infection.

D) We want to prevent any increase in mutation frequency.

The most commonly occurring mutation in people with cystic fibrosis is a deletion of a single codon. This results in A) a base-pair substitution. B) a nucleotide mismatch. C) a frameshift mutation. D) a polypeptide missing an amino acid. E) a nonsense mutation.

D) a polypeptide missing an amino acid.

Which of the following mutations is most likely to cause a phenotypic change? A) a duplication of all or most introns B) a large inversion whose ends are each in intergenic regions C) a nucleotide substitution in an exon coding for a transmembrane domain D) a single nucleotide deletion in an exon coding for an active site E) a frameshift mutation one codon away from the 3' end of the nontemplate strand

D) a single nucleotide deletion in an exon coding for an active site

5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3' Suppose that exposure to a chemical mutagen results in a change in the sequence that alters the 5' end of intron 1 (I1). What might occur? A) loss of the gene product B) loss of E1 C) premature stop to the mRNA D) inclusion of I1 in the mRNA E) exclusion of E2

D) inclusion of I1 in the mRNA

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

D) to translocate polypeptides across the ER membrane

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) It makes a new molecule from its 5' end to its 3' end. C) The process is extremely fast once it is initiated. D) The process occurs in the nucleus of a eukaryotic cell. E) The entire template molecule is represented in the product.

E) The entire template molecule is represented in the product.

Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the A) binding of ribosomes to mRNA. B) shape of the A and P sites of ribosomes. C) bonding of the anticodon to the codon. D) attachment of amino acids to tRNAs. E) bonding of the anticodon to the codon and the attachment of amino acids to tRNAs.

E) bonding of the anticodon to the codon and the attachment of amino acids to tRNAs.

A frameshift mutation could result from A) a base insertion only. B) a base deletion only. C) a base substitution only. D) deletion of three consecutive bases. E) either an insertion or a deletion of a base.

E) either an insertion or a deletion of a base.

Which of the following is the first event to take place in translation in eukaryotes? A) elongation of the polypeptide B) base pairing of activated methionine-tRNA to AUG of the messenger RNA C) binding of the larger ribosomal subunit 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 5' cap of mRNA

E) the small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA

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 the exons B) to the 5' UTR C) to the 3' UTR D) to an adjacent intron and exon E) to the end of an intron

E) to the end of an intron