Chapter 14: Genes
A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is A) 3' UCA 5'. B) 3' UGA 5'. C) 5' TCA 3'. D) 3' ACU 5'. E) either UCA or TCA, depending on wobble in the first base.
A) 3' UCA 5'
DNA template strand 5' _____________________ 3' DNA complementary strand 3' _____________________ 5' Given the locally unwound double strand above, in which direction does the RNA polymerase move? A) 3' → 5' along the template strand B) 5' → 3' along the template strand C) 3' → 5' along the complementary strand D) 5' → 3' along the complementary strand E) 5' → 3' along the double-stranded DNA
A) 3' → 5' along the template strand
The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following? A) A gene from an organism can theoretically be expressed by any other organism. B) All organisms have experienced convergent evolution. C) DNA was the first genetic material. D) The same codons in different organisms translate into the different amino acids. E) Different organisms have different numbers of different types of amino acids.
A) A gene from an organism can theoretically be expressed by any other organism.
Which of the following is not true of RNA processing? A) Exons are cut out before mRNA leaves the nucleus. B) Nucleotides may be added at both ends of the RNA. C) Ribozymes may function in RNA splicing. D) RNA splicing can be catalyzed by spliceosomes. E) A primary transcript is often much longer than the final RNA molecule that leaves the nucleus.
A) Exons are cut out before mRNA leaves the nucleus.
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.
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 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.
A) If UGA, usually a stop codon, is found to code for an amino acid such as tryptophan (usually coded for by UGG only).
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
The anticodon of a particular tRNA molecule is A) complementary to the corresponding mRNA codon. B) complementary to the corresponding triplet in rRNA. C) the part of tRNA that bonds to a specific amino acid. D) changeable, depending on the amino acid that attaches to the tRNA. E) catalytic, making the tRNA a ribozyme.
A) complementary to the corresponding mRNA codon.
A transcription unit that is 8,000 nucleotides long may use 1,200 nucleotides to make a protein consisting of approximately 400 amino acids. This is best explained by the fact that A) many noncoding stretches of nucleotides are present in mRNA. B) there is redundancy and ambiguity in the genetic code. C) many nucleotides are needed to code for each amino acid. D) nucleotides break off and are lost during the transcription process. E) there are termination exons near the beginning of mRNA.
A) many noncoding stretches of nucleotides are present in mRNA.
Garrod hypothesized that "inborn errors of metabolism" such as alkaptonuria occur because A) metabolic enzymes require vitamin cofactors, and affected individuals have significant nutritional deficiencies. B) enzymes are made of DNA, and affected individuals lack DNA polymerase. C) many metabolic enzymes use DNA as a cofactor, and affected individuals have mutations that prevent their enzymes from interacting efficiently with DNA. D) certain metabolic reactions are carried out by ribozymes, and affected individuals lack key splicing factors. E) genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes.
A) metabolic enzymes require vitamin cofactors, and affected individuals have significant nutritional deficiencies.
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-D shape of a DNA molecule
A) the number of hydrogen bonds between A and T in DNA
Which of the following variations on translation would be most disadvantageous for a cell? A) translating polypeptides directly from DNA B) using fewer kinds of tRNA C) having only one stop codon D) lengthening the half-life of mRNA E) having a second codon (besides AUG) as a start codon
A) translating polypeptides directly from DNA
Which component is not directly involved in translation? A) mRNA B) DNA C) tRNA D) ribosomes E) GTP
B) DNA
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.
Which of the following is a function of a poly-A signal sequence? A) It adds the poly-A tail to the 3' end of the mRNA. B) It codes for a sequence in eukaryotic transcripts that signals enzymatic cleavage ~1035 nucleotides away. C) It allows the 3' end of the mRNA to attach to the ribosome. D) It is a sequence that codes for the hydrolysis of the RNA polymerase. E) It adds a 7-methylguanosine cap to the 3' end of the mRNA.
B) It codes for a sequence in eukaryotic transcripts that signals enzymatic cleavage ~1035 nucleotides away.
RNA polymerase in a prokaryote is composed of several subunits. Most of these subunits are the same for the transcription of any gene, but one, known as sigma, varies considerably. Which of the following is the most probable advantage for the organism of such sigma switching? A) It might allow the transcription process to vary from one cell to another. B) It might allow the polymerase to recognize different promoters under certain environmental conditions. C) It could allow the polymerase to react differently to each stop codon. D) It could allow ribosomal subunits to assemble at faster rates. E) It could alter the rate of translation and of exon splicing.
B) It might allow the polymerase to recognize different promoters under certain environmental conditions.
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) It would have no effect, because PKU occurs several steps away in the pathway. B) It would have no effect, because tyrosine is also available from the diet. C) Anyone with PKU must also have alkaptonuria. D) Anyone with PKU is born with a predisposition to later alkaptonuria. E) Anyone with PKU has mild symptoms of alkaptonuria.
B) It would have no effect, because tyrosine is also available from the diet.
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.
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 separate from 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.
B) RNA polymerase transcribes through the terminator sequence, causing the polymerase to separate from the DNA and release the transcript.
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.
What is a ribozyme? A) an enzyme that uses RNA as a substrate B) an RNA with enzymatic activity C) an enzyme that catalyzes the association between the large and small ribosomal subunits D) an enzyme that synthesizes RNA as part of the transcription process E) an enzyme that synthesizes RNA primers during DNA replication
B) an RNA with enzymatic activity
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
In eukaryotic cells, transcription cannot begin until A) the two DNA strands have completely separated and exposed the promoter. B) several transcription factors have bound to the promoter. C) the 5' caps are removed from the mRNA. D) the DNA introns are removed from the template. E) DNA nucleases have isolated the transcription unit.
B) several transcription factors have bound to the promoter.
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.
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' 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
Which of the following does not occur in prokaryotic eukaryotic gene expression, but does in eukaryotic gene expression? A) mRNA, tRNA, and rRNA are transcribed. B) RNA polymerase binds to the promoter. C) A poly-A tail is added to the 3' end of an mRNA and a cap is added to the 5' end. D) Transcription can begin as soon as translation has begun even a little. E) RNA polymerase requires a primer to elongate the molecule.
C) A poly-A tail is added to the 3' end of an mRNA and a cap is added to the 5' end.
The nitrogenous base adenine is found in all members of which group? A) proteins, triglycerides, and testosterone B) proteins, ATP, and DNA C) ATP, RNA, and DNA D) α glucose, ATP, and DNA E) proteins, carbohydrates, and ATP
C) ATP, RNA, and DNA
A part of the promoter, called the TATA box, is said to be highly conserved in evolution. Which of the following 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.
C) Any mutation in the sequence is selected against.
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 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.
During splicing, which molecular component of the spliceosome catalyzes the excision reaction? A) protein B) DNA C) RNA D) lipid E) sugar
C) RNA
In eukaryotes there are several different types of RNA polymerase. Which type is involved in transcription of mRNA for a globin protein? A) ligase B) RNA polymerase I C) RNA polymerase II D) RNA polymerase III E) primase
C) RNA polymerase II
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
n 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
Which of the following provides some evidence that RNA probably evolved before DNA? A) RNA polymerase uses DNA as a template. B) RNA polymerase makes a single-stranded molecule. C) RNA polymerase does not require localized unwinding of the DNA. D) DNA polymerase uses primer, usually made of RNA. E) DNA polymerase has proofreading function.
D) DNA polymerase uses primer, usually made of RNA.
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.
D) It extends from one end of a tRNA molecule.
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.
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
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 3' end
D) a triplet in the same reading frame as an upstream AUG
Transcription in eukaryotes requires which of the following in addition to RNA polymerase? A) the protein product of the promoter B) start and stop codons C) ribosomes and tRNA D) several transcription factors (TFs) E) aminoacyl synthetase
D) several transcription factors (TFs)
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.
Which of the following mutations would be most likely to have a harmful effect on an organism? A) a nucleotide-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
E) a single nucleotide insertion downstream of, and close to, the start of the coding sequence
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
Which of the following statements is false? a)In bacteria, proteins called transcription factors enhance the affinity of RNA polymerase to the promoter sites of genes. b)In bacteria, transcription of a gene is initiated when the RNA polymerase by itself recognizes and binds to the promoter of the gene. c)The initiation of gene transcription in eukaryotes requires the binding of proteins called transcription factors to the TATA box in the promoter region of a gene. d)A relaxation of chromatin packing in eukaryotic cells can facilitate the binding of transcription factors to a promoter of a gene. e)All of the listed responses are correct.
a)In bacteria, proteins called transcription factors enhance the affinity of RNA polymerase to the promoter sites of genes.
Which of the following statements correctly describes mRNA processing? a)Introns are cut out of the primary transcript, and the resulting exons are spliced together. b)Exons are cut out of the primary transcript, and the introns are spliced together. c)Introns are cut out of the primary transcript and spliced together at the end of the transcript. d)Exons are cut out of the primary transcript and transported to the endoplasmic reticulum. e)Introns are cut out of the primary transcript and transported to the ribosomes.
a)Introns are cut out of the primary transcript, and the resulting exons are spliced together.
Which of the following catalyzes the linkage between ribonucleotides to form RNA during gene expression? a)RNA polymerase b)RNA ligase c)a ribozyme d)reverse transcriptase e)tRNA
a)RNA polymerase
In eukaryotes, which of the following mechanisms of gene regulation operates after transcription, but before translation of mRNA into protein? a)RNA splicing b)DNA packaging into nucleosomes c)action of repressors and activators d)protein degradation e)All of the listed responses are correct.
a)RNA splicing
Which of the following is a post-translational modification of a polypeptide? a)cleavage of a polypeptide into two or more chains b)removal of introns and splicing of exons c)formation of a polysome that allows simultaneous formation of many polypeptides from one mRNA transcript d)The growing polypeptide signals the ribosome to attach to the ER. e)complementary base pairing of mRNA and tRNA in the ribosome
a)cleavage of a polypeptide into two or more chains
The function of tRNA during protein synthesis is to _____. a)deliver amino acids to their proper site during protein synthesis b)guide ribosome subunits out of the nucleus through nuclear pores c)attach mRNA to the small subunit of the ribosome d)process mRNA e)transcribe mRNA
a)deliver amino acids to their proper site during protein synthesis
A virus infects a cell and randomly inserts many short segments of DNA containing a stop codon throughout an organism's chromosomes. This will probably cause _____. a)manufactured proteins to be short and defective b)the DNA to break up into thousands of short segments c)incorrect pairing between mRNA codons and amino acids d)no bad effects, as long as the stop codons are not also inserted into tRNA e)All of the listed responses are correct
a)manufactured proteins to be short and defective
Bacteria can transcribe and translate human genes to produce functional human proteins because _____. a)the genetic code is nearly universal b)bacterial ribosomes and eukaryotic ribosomes are identical c)eukaryotes do not really need a nucleus d)RNA has catalytic properties e)bacterial and eukaryotic RNA polymerases are identical
a)the genetic code is nearly universal
What is the proper order of the following events in the expression of a eukaryotic gene? 1. translation 2. RNA processing 3. transcription 4. modification of protein a)1, 2, 3, 4 b)3, 2, 1, 4 c)4, 2, 3, 1 d)2, 3, 4, 1 e)1, 2, 4, 3
b)3, 2, 1, 4
Who formulated the one gene-one enzyme hypothesis? a)Watson and Crick b)Beadle and Tatum c)Hershey and Chase d)Franklin e)None of the listed responses is correct.
b)Beadle and Tatum
What mRNA codon would be made from the DNA triplet CGT? a)ATU b)GCA c)TCU d)CTA e)UCG
b)GCA
The P site of a ribosome does which of the following? a)It holds the tRNA that is carrying the next amino acid to be added to the growing polypeptide chain. b)It holds the tRNA carrying the growing polypeptide chain. c)It helps "unzip" DNA during transcription. d)It catalyzes the addition of amino acids to the tRNAs. e)It recognizes the promoter during transcription initiation.
b)It holds the tRNA carrying the growing polypeptide chain.
A point mutation in which a single base pair is inserted or deleted from DNA is called a(n) _____. a)nonsense mutation b)frame-shift mutation c)inversion mutation d)translocation mutation e)missense mutation
b)frame-shift mutation
A base-pair substitution mutation in a germ cell line is likely to have no effect on phenotype if the substitution _____. a)forms a new stop codon b)occurs in an intron c)changes a stop codon to a codon specifying an amino acid d)changes the structure of an enzyme e)prevents the initiation of transcription of the DNA sequence that codes for ATP synthase
b)occurs in an intron
Generally speaking, how many genetic codes are there? a)20 b)one c)four d)one for each organism e)three
b)one
The codons AAA, CCC, GGG, and UUU specify the amino acids lysine, proline, glycine, and phenylalanine, respectively. What peptide sequence would be encoded by the sequence 5'-CCCAAATTTGGG-3', if present in the coding strand of the DNA? a)lys-pro-gly-phe b)pro-lys-phe-gly c)gly-phe-lys-pro d)phe-gly-pro-lys e)gly-phe-pro-lys
b)pro-lys-phe-gly
Which of the following accurately describes the usual process of transcription for eukaryotic genes? a)Exons are not transcribed. b)Introns are not transcribed. c)Exons are transcribed, but the RNA transcribed from introns does not leave the nucleus. d)Both introns and exons are transcribed, but the RNA transcribed from them does not leave the nucleus. e)Exons and introns are transcribed, and the RNA transcribed from them leaves the nucleus.
c)Exons are transcribed, but the RNA transcribed from introns does not leave the nucleus.
Genetic information of eukaryotic cells is transferred from the nucleus to the cytoplasm in the form of a)proteins b)lipids c)RNA d)carbohydrates e)DNA
c)RNA
When RNA is being made, the RNA base _____ always pairs with the base _____ in DNA. a)U ... T b)T ... G c)U ... A d)A ... U e)T ... A
c)U ... A
Ultraviolet (UV) radiation is damaging to cells because it _____. a)pokes holes in the nuclear envelope b)blocks all translation c)causes mutations in the DNA d)deactivates the enzymes needed for DNA replication e)shreds the cytoskeleton and leads to free radicals
c)causes mutations in the DNA
At one point, as a cell carried out its day-to-day activities, the nucleotides GAT were paired with the nucleotides CUA. This pairing occurred _____. a)in a double-stranded DNA molecule b)during translation c)during transcription d)when an mRNA codon paired with a tRNA anticodon e)It is impossible to say, given this information.
c)during transcription
Polysomes may be defined as _____. a)microfilaments and microtubules b)groups of lysosomes c)groups of ribosomes d)groups of chromosomes e)groups of peroxisomes
c)groups of ribosomes
During the transcription of a given portion of a DNA molecule _____. a)mRNA is synthesized on both chains of the DNA molecule at once b)mRNA is synthesized on both chains of the DNA molecule, but first on one side and then the other c)mRNA is synthesized on only one of the chains d)half of the mRNA is synthesized on half of one chain; then the other half of the mRNA is made on the other half of the DNA e)Any of the listed patterns may be found.
c)mRNA is synthesized on only one of the chains
The first amino acid inserted into a new polypeptide chain in eukaryotic cells is usually _____. a)glycine b)serine c)methionine d)adenosine monophosphate e)alanine
c)methionine
During translation in a eukaryotic cell _____. a)ribosomes move into the nucleus b)tRNA carries amino acid molecules to the nucleus, where they are added to a growing polypeptide chain c)polypeptides are synthesized at ribosomes, according to instructions carried by mRNA d)mRNA is synthesized by the bonding of free nucleotides to the bases on the template strand of DNA e)ribosomes move out of the nucleus
c)polypeptides are synthesized at ribosomes, according to instructions carried by mRNA
In transcription, _____. a)the promoter region acts as an initial binding site for RNA polymerase b)only one of the DNA strands is used as the template c)the RNA nucleotides used are produced by the cell d)All of the listed responses are correct. e)None of the listed responses is correct.
d)All of the listed responses are correct.
Which of the following summaries of protein synthesis is correct? a)DNA transposons leave the nucleus, are transported to a ribosome, and catalyze the polymerization of amino acids in a protein. b)DNA exchanges its thymine units with uracil in polymerase. This activates polymerase, and it starts joining amino acids together. c)Transfer RNAs line up on a ribosome, and amino acids bind to them with hydrogen bonds. d)Messenger RNA is made on a DNA template, and then amino-acid-bearing transfer RNAs bind to it through codon-anticodon pairing. e)DNA strands separate in the nucleus to form mRNA. mRNA leaves the nucleus and is transcribed into tRNA on ribosomes.
d)Messenger RNA is made on a DNA template, and then amino-acid-bearing transfer RNAs bind to it through codon-anticodon pairing.
In many cases, more than one codon codes for the same amino acid. Because of this, we say that the code is _____. a)inaccurate b)incomplete c)not specific d)redundant e)tricky
d)redundant
During translation, amino acid chain elongation occurs until _____. a)no further amino acids are needed by the cell b)all tRNAs are empty c)the polypeptide is long enough d)the ribosome encounters a "stop" codon e)the ribosome runs off the end of the mRNA strand
d)the ribosome encounters a "stop" codon
The number of nucleotide bases "read" together on the mRNA to designate each amino acid is _____; this unit is called a(n) _____. a)two ... dipeptide b)three ... triose c)two ... anticodon d)three ... codon e)one ... amino acid
d)three ... codon
Which of the following statements is true? a)Each DNA base codes for three amino acids. b)Each gene codes for three proteins. c)It takes three genes to code for one protein. d)Each triplet has many different meanings. e)Each amino acid in a protein is coded for by three bases in the DNA.
e)Each amino acid in a protein is coded for by three bases in the DNA.
When genes are expressed, they produce _____. a)enzymes b)RNA molecules c)phenotypic traits d)polypeptides e)The second and fourth responses are correct.
e)The second and fourth responses are correct.
A geneticist found that a particular mutation had no effect on the polypeptide encoded by the gene. This mutation probably involved _____. a)the deletion of one nucleotide b)a missense mutation c)the insertion of one nucleotide d)a nonsense mutation e)a silent or neutral mutation
e)a silent or neutral mutation
Transcription factors are found in _____. a)archaea b)bacteria and eukaryotes c)bacteria and archaea d)eukaryotes e)archaea and eukaryotes
e)archaea and eukaryotes
How many nucleotides are needed to code for a protein with 450 amino acids? a)at least 150 b)at least 300 c)at least 450 d)at least 900 e)at least 1,350
e)at least 1,350
The bonds that hold tRNA molecules in the correct three-dimensional shape are _____. a)peptide linkages b)hydrophobic interactions c)covalent bonds d)ionic bonds e)hydrogen bonds
e)hydrogen bonds
In a eukaryotic cell, transcription takes place _____. a)on the cell membrane b)in the rough endoplasmic reticulum c)in the cytoplasm d)on free ribosomes e)in the nucleus
e)in the nucleus
One strand of a DNA molecule has the following sequence: 3'-AGTACAAACTATCCACCGTC-5'. In order for transcription to occur in that strand, there would have to be a specific recognition sequence, called a(n) _____, to the left of the DNA sequence indicated. a)centromere b)intron c)exon d)AUG codon e)promoter
e)promoter
