Bio 13

The flow of information in a cell proceeds in what sequence? A. from DNA to protein to RNA B. from RNA to DNA to protein C. from DNA to RNA to protein D. from protein to RNA to DNA E. from RNA to protein to DNA

C

The following question refers to this figure of a simple metabolic pathway: According to Beadle and Tatum's hypothesis, how many genes are necessary for this pathway? 0 1 2 3

2

Use the following information to answer the question.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? 3 6 9 27 81

27

After an RNA molecule is transcribed from a eukaryotic gene, what are removed and what are spliced together to produce an mRNA molecule with a continuous coding sequence? A. introns ... exons B. exons ... introns C. operators ... promoters D. silencers ... enhancers E. promoters ... operators

A

In eukaryotic cells, transcription cannot begin until A. several transcription factors have bound to the promoter. B. the 5' caps are removed from the mRNA. C. DNA nucleases have isolated the transcription unit. D. the two DNA strands have completely separated and exposed the promoter. E. the DNA introns are removed from the template.

A

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. One altered tRNA molecule will be relatively inconsequential because it will compete with many "normal" ones. B. The altered tRNA will result in an amino acid variant in all copies of the protein. C. The altered tRNA will be so unstable that it will not participate in translation. D. The altered tRNA will cause this mRNA to make only nonfunctioning product. E. The tRNA-Leu will not be able to enter the ribosome to bind to the UUA codon.

A

The following question refers to this table of codons. 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. 5' TTT-CCC-AAA-GGG-TTT-CCC B. 3' AUG-AAA-GGG-TTT-CCC-AAA-GGG C. 3' UUU-CCC-AAA-GGG-UUU-CCC D. 5' GGG-AAA-TTT-AAA-CCC-ACT-GGG E. 5' ACT-TAC-CAT-AAA-CAT-TAC-UGA

A

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

A

Use the following model of a eukaryotic transcript to answer the question. 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' UTR E1 E2 E3 E4 UTR 3' B. 5' E1 I1 E2 I2 E3 I3 E4 3' C. 5' UTR I1 I2 I3 UTR 3' D. 5' I1 I2 I3 3' E. 5' E1 E2 E3 E4 3'

A

Use the following model of a eukaryotic transcript to answer the question. 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 end of an intron B. to the 5' UTR C. to the 3' UTR D. to the exons E. to an adjacent intron and exon

A

Using Figure 17.5 in your textbook, 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'-CTTCGGGAA-3' B. 5'-UUUGGGAAA-3' C. 5'-AAACCCUUU-3' D. 5'-GAACCCCTT-3' E. 5'-AAAACCTTT-3'

A

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

A

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

A

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 prevents supercoiling of the DNA near the start site. C. It sets the reading frame of the mRNA. D. Its significance has not yet been determined. E. It is the recognition site for ribosomal binding.

A

Which of the following mutations would likely be most dangerous to a cell? A. Deletion of one nucleotide B. Substitution of one nucleotide for another C. Deletion of three nucleotides

A

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 two nucleotides B. an insertion of a codon C. a substitution of the first nucleotide of a GGG codon D. a substitution of the third nucleotide in an ACC codon E. a deletion of a codon

A

Which of these is currently considered the best definition of a gene? A. A gene codes for either a polypeptide or an RNA molecule. B. A gene codes for a single enzyme. C. A gene codes for a single polypeptide. D. A gene codes for a single protein. E. A gene codes for a particular ribozyme.

A

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 start of a gene B. a base substitution C. deletion of three bases near the start of the coding sequence, but not in the initiator codon D. a base insertion near the end of the coding sequence, but not in the terminator codon E. a base deletion near the end of the coding sequence, but not in the terminator codon

A

Which of the following statements about ribozymes is/are correct? Select all that apply. A. A ribosome can be regarded as one large ribozyme. B. Ribozymes are RNA molecules that function as enzymes. C. In some genes, intron RNA functions as a ribozyme and catalyzes its own excision.

ABC

Which of the following molecules are produced by transcription? Select all that apply. A. Ribozymes B. Ribosomal proteins C. Messenger RNA

AC

A codon consists of _____ bases and specifies which _____ will be inserted into the polypeptide chain. A. four ... amino acid B. three ... amino acid C. three ... nucleotide D. two ... nucleotide E. four ... fatty acid

B

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

B

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 is transcribed at the start of every gene. B. Any mutation in the sequence is selected against. C. The sequence does not mutate. D. The sequence is found in many but not all promoters. E. The sequence evolves very rapidly.

B

Alternative RNA splicing A. can allow the production of similar proteins from different RNAs. B. can allow the production of proteins of different sizes and functions from a single mRNA. C. is a mechanism for increasing the rate of transcription. D. increases the rate of transcription. E. is due to the presence or absence of particular snRNPs.

B

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 plasma membrane, where it causes exocytosis. B. Its signal sequence must target it to the ER, after which it goes to the Golgi. C. Its signal sequence must be cleaved off before the polypeptide can enter the ER. D. Its signal sequence must cause it to be encased in a vesicle as soon as it is translated. E. It must be translated by a ribosome that remains free of attachment to the ER.

B

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

B

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

B

In eukaryotes there are several different types of RNA polymerase. Which type is involved in transcription of mRNA for a globin protein? A. RNA polymerase III B. RNA polymerase II C. primase D. ligase E. RNA polymerase I

B

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. eukaryotic tRNAs B. a bacterial promoter sequence C. the introns D. eukaryotic ribosomal subunits E. eukaryotic polymerases

B

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

B

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 several codons are found to translate to the same amino acid, such as serine. 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 prokaryotic organisms are able to translate a eukaryotic mRNA and produce the same polypeptide. D. If a single mRNA molecule is found to translate to more than one polypeptide when there are two or more AUG sites. E. If one stop codon, such as UGA, is found to have a different effect on translation than another stop codon, such as UAA.

B

The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following? A. The same codons in different organisms translate into the different amino acids. B. A gene from an organism can theoretically be expressed by any other organism. C. DNA was the first genetic material. D. All organisms have experienced convergent evolution. E. Different organisms have different numbers of different types of amino acids.

B

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

B

What is the function of RNA polymerase? A. It proceeds slowly along the DNA strand, requiring about a minute to add two nucleotides to the growing mRNA molecule. B. It unwinds the double helix and adds nucleotides to a growing strand of RNA. C. It adds nucleotides to the 5' end of the growing mRNA molecule. D.It relies on other enzymes to unwind the double helix. E. All of the above.

B

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

B

Which of the following is true of transcription in domain Archaea? A. It involves promoters are identical to those in domain Eukarya. B. There is only one kind of RNA polymerase. C. It produces RNA transcripts that are processed after they leave the nucleus. D. It terminates in a manner similar to that in bacteria. E. It is regulated in the same way as in domain Bacteria.

B

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 a stop codon, causing the polymerase to stop advancing through the gene and release the mRNA. D. Once transcription has initiated, RNA polymerase transcribes until it reaches the end of the chromosome. E. RNA polymerase transcribes through an intron, and the snRNPs cause the polymerase to let go of the transcript.

B

A eukaryotic 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 nucleotides are needed to code for each amino acid. B. there are termination exons near the beginning of mRNA. C. many noncoding stretches of nucleotides are present in eukaryotic DNA. D. there is redundancy and ambiguity in the genetic code. E. nucleotides break off and are lost during the transcription process.

C

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. the cell will compensate for the defect by attaching phenylalanine to tRNAs with lysine-specifying anticodons. B. none of the options will occur; the cell will recognize the error and destroy the tRNA. C. proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU. D. the ribosome will skip a codon every time a UUU is encountered. E. none of the proteins in the cell will contain phenylalanine.

C

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

C

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

C

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

C

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 variability in RNA polymerase? A. It could allow ribosomal subunits to assemble at faster rates. B. It might allow the translation process to vary from one cell to another. C. It might allow the polymerase to recognize different promoters under certain environmental conditions. D. It could alter the rate of translation and of exon splicing. E. It could allow the polymerase to react differently to each stop codon.

C

The average length of a transcription unit along a eukaryotic DNA molecule is about 27,000 nucleotide pairs, whereas an averaged-sized protein is about 400 amino acids long. What is the best explanation for this fact? A. Each amino acid in a protein is encoded by a triplet of nucleotides. B. Many genes are subject to alternative RNA splicing. C. Most eukaryotic genes and their RNA transcripts have long noncoding stretches of nucleotides that are not translated.

C

The following question refers to this table of codons. A possible sequence of nucleotides in the template strand of DNA that would code for the polypeptide sequence phe-leu-ile-val would be A. 5' TTG-CTA-CAG-TAG 3'. B. 3' AAA-AAT-ATA-ACA 5'. C. 3' AAA-GAA-TAA-CAA 5'. D. 5' AUG-CTG-CAG-TAT 3'. E 3' AAC-GAC-GUC-AUA 5'.

C

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 polypeptide missing an amino acid. D. a nonsense mutation. E. a frameshift mutation.

C

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. competitive exclusion forces some tRNAs to be destroyed by nucleases. C. the rules for base pairing between the third base of a codon and tRNA are flexible. D. many codons are never used, so the tRNAs that recognize them are dispensable. E. the DNA codes for all 61 tRNAs but some are then destroyed.

C

Use the following information to answer the question. 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) in the ribosome already. Where does tRNA #2 move to after this bonding of lysine to the polypeptide? A. P site B. A site C. E site D. directly to the cytosol E. exit tunnel

C

Use the following information to answer the question. 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) in the ribosome already. Which component of the complex described enters the exit tunnel through the large subunit of the ribosome? A. initiation and elongation factors B. tRNA that no longer has attached amino acid C. newly formed polypeptide D. tRNA with attached lysine (#1) E. tRNA with polypeptide (#2)

C

Use the following model of a eukaryotic transcript to answer the question. 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. exclusion of E2 B. loss of E1 C. inclusion of I1 in the mRNA

C

Use the following model of a eukaryotic transcript to answer the question. 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. Introns protect exon structure. B. Each intron has enzymatic properties. C. Introns allow exon shuffling. D. They are translated into small polypeptides. E. They become parts of snRNPs.

C

Use the following model of a eukaryotic transcript to answer the question. 5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3' Suppose that an induced mutation removes most of the 5' end of the 5' UTR. What might result? A. The 3' UTR will duplicate and one copy will replace the 5' end. B. Removal of the 5' UTR will result in the strand not binding to tRNAs. C. Removal of the 5' UTR also removes the 5' cap and the mRNA will quickly degrade. D. Removal of the 5' UTR has no effect because the exons are still maintained. E. The first exon will not be read because I1 will now serve as the UTR.

C

What is the function of the release factor (RF)? A. It releases the ribosome from the eR to allow polypeptides into the cytosol. B. It separates tRNA in the A site from the growing polypeptide. C. It binds to the stop codon in the A site in place of a tRNA. D. It releases the amino acid from its tRNA to allow the amino acid to form a peptide bond. E. It supplies a source of energy for termination of translation.

C

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 separated polypeptide B. separated ribosomal subunits, a polypeptide, and free tRNA C. an assembled ribosome with a polypeptide attached to the tRNA in the P site D. a cell with fewer ribosomes E. separated ribosomal subunits with a polypeptide attached to the tRNA

C

When the spliceosome binds to this transcript, where can it attach? A. to the 5' UTR B. to an adjacent intron and exon C. at certain sites along an intron D. to the exons E. to the 3' UTR

C

Where does RNA polymerase begin transcribing a gene into mRNA? A. Transfer RNA acts to translate the message to RNA polymerase. B. It looks for the AUG start codon. C. It starts after a certain nucleotide sequence called a promoter. D. It starts at one end of the chromosome. E. The ribosome directs it to the correct portion of the DNA molecule.

C

Which of the following DNA mutations is the most likely to be damaging to the protein it specifies? A. a codon substitution B. a codon deletion C. a base-pair deletion D. a substitution in the last base of a codon E. a point mutation

C

Which of the following is a function of a poly-A signal sequence? A. It is a sequence that codes for the hydrolysis of the RNA polymerase. B. It adds a 7-methylguanosine cap to the 3' end of the mRNA. C. It codes for a sequence in eukaryotic transcripts that signals enzymatic cleavage ~10-35 nucleotides away. D. It allows the 3' end of the mRNA to attach to the ribosome. E. It adds the poly-A tail to the 3' end of the mRNA.

C

Which of the following is not true of RNA processing? A. RNA splicing can be catalyzed by spliceosomes. B. Nucleotides may be added at both ends of the RNA. C. Exons are cut out before mRNA leaves the nucleus. D. A primary transcript is often much longer than the final RNA molecule that leaves the nucleus. E. Ribozymes may function in RNA splicing.

C

Which of the following is not true of a codon? A. It consists of three nucleotides. B. It is the basic unit of the genetic code. C. It extends from one end of a tRNA molecule. D. It may code for the same amino acid as another codon. E. It never codes for more than one amino acid.

C

Why might a point mutation in DNA make a difference in the level of a protein's activity? A. It might result in a chromosomal translocation. B. It might exchange one serine codon for a different serine codon. C. It might substitute a different amino acid in the active site. 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.

C

Garrod hypothesized that "inborn errors of metabolism" such as alkaptonuria occur because A. certain metabolic reactions are carried out by ribozymes, and affected individuals lack key splicing factors. 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. genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes. E. metabolic enzymes require vitamin cofactors, and affected individuals have significant nutritional deficiencies.

D

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 is born with a predisposition to later alkaptonuria. B. Anyone with PKU must also have alkaptonuria. C. It would have no effect, because PKU occurs several steps away in the pathway. D. It would have no effect, because tyrosine is also available from the diet. E. Anyone with PKU has mild symptoms of alkaptonuria.

D

Use this representation to answer the following question. DNA template strand 5' ____________________________ 3' DNA complementary strand 3' ____________________________ 5' In the transcription event of the previous DNA, where would the promoter be located? A. to the left of the template strand B. to the right of the non-template strand C. to the left of the non-template strand D. to the right of the template strand E. at the 3' end of the newly made RNA

D

What does a mutagen cause? A. problems with mitosis B. a reduction in the number of tRNA molecules available for protein synthesis C. decreased permeability of the nuclear envelope D. a change in the sequence of DNA E. decreased enzyme activity throughout the cell

D

What is a ribozyme? A. a mutated ribosome B. a biological catalyst consisting of DNA C. an enzyme that holds open the DNA double helix while RNA polymerase adds nucleotides D. a biological catalyst made of RNA E. a DNA sequence near the promoter that assists in the binding of RNA polymerase

D

What type of bonding is responsible for maintaining the shape of the tRNA molecule? A. van der Waals interactions between hydrogen atoms B. covalent bonding between sulfur atoms C. peptide bonding between amino acids D. hydrogen bonding between base pairs E. ionic bonding between phosphates

D

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

D

Which of the following is a function of a signal peptide? A. to bind RNA polymerase to DNA and initiate transcription B. to signal the initiation of transcription C. to terminate translation of the messenger RNA D. to translocate polypeptides across the ER membrane E. to direct an mRNA molecule into the cisternal space of the ER

D

Which of the following nucleotide triplets best represents a codon? A. a sequence in tRNA at the 3' end B. a triplet separated spatially from other triplets 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 triplet that has no corresponding amino acid

D

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

D

Which one of the following is true of tRNAs? A. tRNAs are double-stranded. B. There are four types of tRNA. C. tRNAs carry special sequences known as codons. D. Each tRNA binds a particular amino acid. E. All of the above.

D

A simple metabolic pathway is shown below. A mutation results in a defective enzyme A. Which of the following would be a consequence of that mutation? A. an accumulation of B and no production of A and C B. an accumulation of B and C and no production of A C. an accumulation of C and no production of A and B D. an accumulation of A and B and no production of C E. an accumulation of A and no production of B and C

E

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

E

How is translation initiated? A. The small ribosomal subunit binds to the mRNA. B. The tRNA bearing methionine binds to the start codon. C. The large ribosomal subunit binds to the small one. D. The start codon signals the start of translation. E. All of the above.

E

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 C only C. minimal medium supplemented with nutrient A only D. minimal medium supplemented with nutrients A and C E. minimal medium supplemented with nutrient B only

E

RNA polymerase moves in which direction along the DNA? A. 5' to 3' along the double-stranded DNA B. 3' to 5' along the nontemplate strand C. 5' to 3' along the template strand D. 5' to 3' along whichever strand it's on E. 3' to 5' along the template strand

E

The following information should be used for the questions. A part of an mRNA molecule with the following sequence is being read by a ribosome: 5' CCG-ACG 3' (mRNA). The following charged transfer RNA molecules (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. The anticodon loop of the first tRNA that will complement this mRNA is A. 3' UGC 5' B. 5' GGC 3' C. 5' ACG 3' D. 5' UGC 3' E. 3' GGC 5'

E

The following question refers to this table of codons. 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-glu-arg-arg-glu-leu C. met-arg-glu-arg-glu-arg D. met-leu-phe-arg-glu-glu E. met-ser-ser-leu-ser-leu

E

The nitrogenous base adenine is found in all members of which group? A. proteins, triglycerides, and testosterone B. α glucose, ATP, and DNA C. proteins, carbohydrates, and ATP D. proteins, ATP, and DNA E. ATP, RNA, and DNA

E

Use this representation to answer the following question. 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. 5' → 3' along the template strand B. 5' → 3' along the double-stranded DNA C. 5' → 3' along the complementary strand D. 3' → 5' along the complementary strand E. 3' → 5' along the template strand

E

Which component is not directly involved in translation? A. GTP B. ribosomes C. tRNA D. mRNA E. DNA

E

Which of the following experimental procedures is most likely to hasten mRNA degradation in a eukaryotic cell? A. methylation of C nucleotides B. removal of one or more exons C. methylation of histones D. enzymatic lengthening of the poly-A tail E. removal of the 5' cap

E

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

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

E

Which of the following mutations would be most likely to have a harmful effect on an organism? A. a single nucleotide deletion near the end of the coding sequence B. a nucleotide-pair substitution C. a single nucleotide deletion in the middle of an intron D. a deletion of three nucleotides near the middle of a gene E. a single nucleotide insertion downstream of, and close to, the start of the coding sequence

E

Which of the following provides some evidence that RNA probably evolved before DNA? A. DNA polymerase has proofreading function. B. RNA polymerase makes a single-stranded molecule. C. RNA polymerase uses DNA as a template. D. RNA polymerase does not require localized unwinding of the DNA. E. DNA polymerase uses primer, usually made of RNA.

E

The figure 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? UGG UUC GUA CAU GUG

UUC

The anticodon of a particular tRNA molecule is A. the part of tRNA that bonds to a specific amino acid. B. complementary to the corresponding triplet in rRNA. C. catalytic, making the tRNA a ribozyme. D. changeable, depending on the amino acid that attaches to the tRNA. E. complementary to the corresponding mRNA codon.

e

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 supplemented with C only B. minimal medium supplemented with nutrients A and B C. minimal medium supplemented with A only D. minimal medium E. minimal medium supplemented with B only

A

The following information should be used for the question. A part of an mRNA molecule with the following sequence is being read by a ribosome: 5' CCG-ACG 3' (mRNA). The following charged transfer RNA molecules (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. The dipeptide that will form will be A. proline-threonine. B. cysteine-alanine. C. glycine-cysteine. D. alanine-alanine. E. threonine-glycine.

A

What is a ribozyme? A. an RNA with enzymatic activity B. an enzyme that synthesizes RNA primers during DNA replication C. an enzyme that uses RNA as a substrate D. an enzyme that catalyzes the association between the large and small ribosomal subunits E. an enzyme that synthesizes RNA as part of the transcription process

A

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' ACU 5'. B. 3' UCA 5'. C. 5' TCA 3'. D. 3' UGA 5'. E. either UCA or TCA, depending on wobble in the first base.

B

Transcription in eukaryotes requires which of the following in addition to RNA polymerase? A. the protein product of the promoter B. several transcription factors C. aminoacyl-tRNA synthetase D. ribosomes and tRNA E. start and stop codons

B

Which of the following molecules is/are produced by translation? Include molecules that are subject to further modification after initial synthesis. Select all that apply. A. The amino acid glycine B. RNA polymerase C. Aminoacyl-tRNA synthetase

BC

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

D

The tRNA shown in the figure has its 3' end projecting beyond its 5' end. What will occur at this 3' end? A. The excess nucleotides (ACCA) will be cleaved off at the ribosome. B. The small and large subunits of the ribosome will attach to it. C. The 5' cap of the mRNA will become covalently bound. D. The amino acid binds covalently. E. The codon and anticodon complement one another.

D

Use the following information to answer the question. The enzyme polynucleotide phosphorylase randomly assembles nucleotides into a polynucleotide polymer. You add polynucleotide phosphorylase to a solution of adenosine triphosphate and guanosine triphosphate. How many artificial mRNA 3 nucleotide codons would be possible? 3 4 8 16 64

8

During splicing, which molecular component of the spliceosome catalyzes the excision reaction? A.sugar B. DNA C. protein D. lipid E. RNA

E