Chapter 7
T/F In bacteria, most protein-coding genes lack introns.
True
T/F RNA polymerases can start an RNA chain without a primer
True
T/F Some genes do not encode proteins, but instead encode functional RNA.
True
T/F Unlike the coding sequence of an exon, most of the nucleotide sequence of an intron is unimportant.
True
Below is the sequence from the 3′ end of an mRNA. 5′-CCGUUACCAGGCCUCAUUAUUGGUAACGGAAAAAAAAAAAAAA-3′ If you were told that this sequence contains the stop codon for the protein encoded by this mRNA, what is the anticodon on the tRNA in the P-site of the ribosome when release factor binds to the A-site? a. 5′-CCA-3′ b. 5′-CCG-3′ c. 5′-UGG-3′ d. 5′-UUA-3′
a. 5′-CCA-3′
What is a polyribosome? a. A cluster of ribosomes translating the same mRNA, but positioned at different sites along the mRNA. b. A ribosome that is in the middle of translating an mRNA into a polypeptide. c. A ribosome translating a polycistronic mRNA molecule.
a. A cluster of ribosomes translating the same mRNA, but positioned at different sites along the mRNA.
At what site do all charged tRNAs (with the exception of the initiator tRNA) first bind on the ribosome? a. A site b. P site c. E site
a. A site
How do proteases act? a. By hydrolyzing peptide bonds between amino acids in a protein b. By forming peptide bonds between amino acids in a protein c. By folding polypeptides into correct three dimensional structures
a. By hydrolyzing peptide bonds between amino acids in a protein
Transcription in bacteria differs from transcription in a eucaryotic cell because __________________________. a. RNA polymerase (along with its sigma subunit) can initiate transcription on its own b. RNA polymerase (along with its sigma subunit) requires the general transcription factors to assemble at the promoter before polymerase can begin transcription c. The sigma subunit must associate with the appropriate type of RNA polymerase to produce mRNAs d. RNA polymerase must be phosphorylated at its C-terminal tail for transcription to proceed
a. RNA polymerase (along with its sigma subunit) can initiate transcription on its own
Which of the following statements about the Lac operon is FALSE? a. The Lac repressor binds when lactose is present in the cell. b. Even when the CAP activator is bound to DNA, if lactose is not present, the Lac operon will not be transcribed. c. The CAP activator can only bind DNA when it is bound to cAMP. d. The Lac operon only produces RNA when lactose is present and glucose is absent.
a. The Lac repressor binds when lactose is present in the cell.
The assembly of general transcription factors to a eukaryotic promoter begins at what site in a promoter? a. The TATA box b. The GAGA box c. The TFIID box d. The assembly box
a. The TATA box
Which of the following does not occur before a eukaryotic mRNA is exported from the nucleus? a. The ribosome binds to the mRNA. b. The mRNA is polyadenylated at its 3′ end. c. 7-methyl-G is added in a 5′ to 5′ linkage to the mRNA. d. RNA polymerase dissociates.
a. The ribosome binds to the mRNA.
Which of the following statements about transcriptional regulators is FALSE? a. Transcriptional regulators usually interact with the sugar-phosphate backbone on the outside of the double helix to determine where to bind on the DNA helix. b. Transcriptional regulators will form hydrogen bonds, ionic bonds, and hydrophobic interactions with DNA. c. The DNA-binding motifs of transcriptional regulators usually bind in the major groove of the DNA helix. d. The binding of transcriptional regulators generally does not disrupt the hydrogen bonds that hold the double helix together.
a. Transcriptional regulators usually interact with the sugar-phosphate backbone on the outside of the double helix to determine where to bind on the DNA helix.
Amino acids are attached to their tRNA molecules by: a. aminoacyl-tRNA synthetase. b. peptide bond formation. c. RNA ligase. d. aminoacyl hydroxylases.
a. aminoacyl-tRNA synthetase
Eukaryotic mRNAs: a. are translated after they are exported from the nucleus. b. are transcribed and translated simultaneously. c. must be folded into the correct three-dimensional shape before they can be translated. d. are processed in the same way as prokaryotic mRNAs.
a. are translated after they are exported from the nucleus.
What determines the nucleotide sequence of an RNA strand? a. complementary base pairing with the DNA template during transcription b. the amino acid sequence in a protein c. the diversity of nucleotides accessible to RNA polymerase to use in transcription
a. complementary base pairing with the DNA template during transcription
An RNA molecule can fold into complex three-dimensional shapes because: a. it is single-stranded b. it is double-stranded c. it contains the base uracil rather than thymine
a. it is single-stranded
Which amino acid would you expect a tRNA with the anticodon 5′-CUU-3′ to carry? a. lysine b. glutamic acid c. leucine d. phenylalanine
a. lysine
RNA polymerases join nucleotides through what kind of bond? a. phosphodiester b. Hydrogen c. Peptide d. Glycosidic
a. phosphodiester
To being transcription, RNA polymerase recognizes nucleotide sequences in what region of the DNA? a. promoter region b. Template region c. G-C rich region d. Terminator region
a. promoter region
How many nucleotides are necessary to specify a single amino acid? a. 1 b. 3 c. 20 d. it depends on the amino acid
b. 3
In principle, how many reading frames in RNA can potentially be translated into proteins? a. 1 b. 3 c. 4 d. 6
b. 3
An RNA chain elongates in what direction? a. 3' to 5' b. 5' to 3'
b. 5' to 3'
You have a piece of DNA that includes the following sequence: 5′-ATAGGCATTCGATCCGGATAGCAT-3′ 3′-TATCCGTAAGCTAGGCCTATCGTA-5′ Which of the following RNA molecules could be transcribed from this piece of DNA? a. 5′-UAUCCGUAAGCUAGGCCUAUGCUA-3′ b. 5′-AUAGGCAUUCGAUCCGGAUAGCAU-3′ c. 5′-UACGAUAGGCCUAGCUUACGGAUA-3′ d. none of the above
b. 5′-AUAGGCAUUCGAUCCGGAUAGCAU-3′
In a diploid organism, the DNA encoding one of the tRNAs for the amino acid tyrosine is mutated such that the sequence of the anticodon is now 5′-CTA-3′ instead of 5′-GTA-3′. What kind of aberration in protein synthesis will this tRNA cause? Use the codon table provided below to answer this question. a. In-frame deletion b. A shorter protein will be made c. A longer protein will be made d. Silent mutation (i.e. no change)
b. A shorter protein will be made
The translation of an mRNA begins at the start codon: a. AGU b. AUG c. UAG d. ATG
b. AUG
Which sugar cannot be readily made from formaldehyde in experiments simulating conditions on primitive Earth? a. Ribose b. Deoxyribose c. Glucose
b. Deoxyribose
Which of the following statements about RNA splicing is false? a. Conventional introns are not found in bacterial genes. b. For a gene to function properly, every exon must be removed from the primary transcript in the same fashion on every mRNA molecule produced from the same gene. c. Small RNA molecules in the nucleus perform the splicing reactions necessary for the removal of introns. d. Splicing occurs after the 5′ cap has been added to the end of the primary transcript.
b. For a gene to function properly, every exon must be removed from the primary transcript in the same fashion on every mRNA molecule produced from the same gene.
In eucaryotes, what must assemble at a promoter before RNA polymerase can transcribe a gene? a. Nucleotides required in transcription b. General transcription factors c. Sigma factor d. An RNA primer
b. General transcription factors
Which of the following statements is NOT true? a. The different lifetimes of eukaryotic mRNAs are controlled in part by nucleotide sequences in the mRNA itself. b. In a eukaryotic mRNA, the poly-A tail promotes degradation of the molecule. c. Many eukaryotic mRNAs have a longer lifetime than bacterial mRNAs. d. The longer the lifetime of an mRNA, the more protein can be produced from it.
b. In a eukaryotic mRNA, the poly-A tail promotes degradation of the molecule.
A poison added to an in vitro translation mixture containing mRNA molecules with the sequence 5′-AUGAAAAAAAAAAAAUAA-3′ has the following effect: the only product made is a Met-Lys dipeptide that remains attached to the ribosome. What is the most likely way in which the poison acts to inhibit protein synthesis? a. It inhibits peptidyl transferase activity. b. It inhibits movement of the small subunit relative to the large subunit. c. It inhibits release factor. d. It mimics release factor.
b. It inhibits movement of the small subunit relative to the large subunit.
At what site does the charged initiator tRNA first bind on the ribosome? a. A site b. P site c. E site
b. P site
There are several reasons why the primase used to make the RNA primer for DNA replication is not suitable for gene transcription. Which of the statements below is not one of those reasons? a. Primase initiates RNA synthesis on a single-stranded DNA template. b. Primase can initiate RNA synthesis without the need for a base-paired primer. c. Primase synthesizes only RNAs of about 5-20 nucleotides in length. d. The RNA synthesized by primase remains base-paired to the DNA template.
b. Primase can initiate RNA synthesis without the need for a base-paired primer.
Which type of molecule has the potential to perform the catalytic action of reproducing itself? a. DNA b. RNA c. Protein d. Polysaccharides
b. RNA
You are studying a disease that it caused by a virus, but when you purify the virus particles and analyze them you find they contain no trace of DNA. Which of the following molecules are likely to contain the genetic information of the virus? a. high-energy phosphate groups b. RNA c. lipids d. carbohydrates
b. RNA
Introns are removed by: a. RNase. b. RNA splicing in the nucleus. c. RNA splicing in the cytoplasm. d. RNA polymerase III.
b. RNA splicing in the nucleus
Which statement is false? a. The genetic code contains three stop codons. b. Stop codons are not recognized by a tRNA. c. Release factors bind to stop codons.
b. Stop codons are not recognized by a tRNA.
You have a bacterial strain with a mutation that removes the transcription termination signal from the Abd operon. Which of the following statements describes the most likely effect of this mutation on Abd transcription? a. The Abd RNA will not be produced in the mutant strain. b. The Abd RNA from the mutant strain will be longer than normal. c. Sigma factor will not dissociate from RNA polymerase when the Abd operon is being transcribed in the mutant strain. d. RNA polymerase will move in a backwards fashion at the Abd operon in the mutant strain.
b. The And RNA from the mutant strain will be longer than normal.
Which of the following statements about the genetic code is correct? a. All codons specify more than one amino acid. b. The genetic code is redundant. c. All amino acids are specified by more than one codon. d. All codons specify an amino acid.
b. The genetic code is redundant.
The sigma subunit of bacterial RNA polymerase ___________________. a. contains the catalytic activity of the polymerase b. remains part of the polymerase throughout transcription c. recognizes promoter sites in the DNA d. recognizes transcription termination sites in the DNA
c. recognizes promoter sites in the DNA
An RNA message is decoded by: a. ribozymes b. RNA polymerases c. ribosomes d. the nucleus
c. ribosomes
What is the name of the subunit of bacterial RNA polymerase that recognizes the promoter of a gene? a. α helix b. β polymerase c. sigma factor
c. sigma factor
The concentration of a particular protein X in a normal human cell rises gradually from a low point, immediately after cell division, to a high point, just before cell division, and then drops sharply. The level of its mRNA in the cell remains fairly constant throughout this time. Protein X is required for cell growth and survival, but the drop in its level just before cell division is essential for division to proceed. You have isolated a line of human cells that grow in size in culture but cannot divide, and on analyzing these mutants, you find that levels of X mRNA in the mutant cells are normal. Which of the following mutations in the gene for X could explain these results? a. the introduction of a stop codon that truncates protein X at the fourth amino acid b. a change of the first ATG codon to CCA c. the deletion of a sequence that encodes sites at which ubiquitin can be attached to the protein d. a change at a splice site that prevents splicing of the RNA
c. the deletion of a sequence that encodes sites at which ubiquitin can be attached to the protein
What energy drives the transcription reaction forward? a. The release of high-energy electrons from cofactors associated with RNA polymerase b. The energy from ATP formation c. the hydrolysis of high-energy bonds of ribonucleoside triphosphate during elongation
c. the hydrolysis of high-energy bonds of ribonucleoside triphosphate during elongation
All of the RNA in a cell is made by what process? a. replication b. hydrolysis c. transcription d. translation
c. transcription
An extraterrestrial organism (ET) is discovered whose basic cell biology seems pretty much the same as that of terrestrial organisms except that it uses a different genetic code to translate RNA into protein. You set out to break the code by translation experiments using RNAs of known sequence and cell-free extracts of ET cells to supply the necessary protein-synthesizing machinery. In experiments using the RNAs below, the following results were obtained when the 20 possible amino acids were added either singly or in different combinations of two or three: RNA 1: 5′-GCGCGCGCGCGCGCGCGCGCGCGCGCGC-3′ RNA 2: 5′-GCCGCCGCCGCCGCCGCCGCCGCCGCCGCC-3′ Using RNA 1, a polypeptide was produced only if alanine and valine were added to the reaction mixture. Using RNA 2, a polypeptide was produced only if leucine and serine and cysteine were added to the reaction mixture. Assuming that protein synthesis can start anywhere on the template, that the ET genetic code is non-overlapping and linear, and that each codon is the same length (like the terrestrial triplet code), how many nucleotides does an ET codon contain? a. 2 b. 3 c. 4 d. 5 e. 6
d. 5
One strand of a section of DNA isolated from the bacterium E. coli reads: 5′-ATGGTAGCCTACCCATAGG-3′ What will be the sequence of the mRNA in this region? Use the codon table provided in question 41 to answer this question. a. 5'-CCUAUGGGUAGGCUACCAU-3' b. 5'-GUAGCCUACCCAUAGG-3' d. 5′-ATGGTAGCCTACCCATAGG-3′ d. 5′-AUGGUAGCCUACCCAUAGG-3′
d. 5′-AUGGUAGCCUACCCAUAGG-3′
You have discovered an alien life form that surprisingly uses DNA as its genetic material, makes RNA from DNA, and reads the information from RNA to make protein using ribosomes and tRNAs, which read triplet codons. Because it is your job to decipher the genetic code for this alien, you synthesize some artificial RNA molecules and examine the protein products produced from these RNA molecules in a cell-free translation system using purified alien tRNAs and ribosomes. You obtain the results shown in the following table: From this information, which of the following peptides can be produced from poly UAUC? a. Ile-Phe-Val-Tyr b. Tyr-Ser-Phe-Ala c. Ile-Lys-His-Tyr d. Cys-Pro-Lys-Ala
d. Cys-Pro-Lys-Ala
Which of the following methods is NOT used by cells to regulate the amount of a protein in the cell? a. Genes can be transcribed into mRNA with different efficiencies. b. Many ribosomes can bind to a single mRNA molecule. c. Proteins can be tagged with ubiquitin, marking them for degradation. d. Nuclear pore complexes can regulate the speed at which newly synthesized proteins are exported from the nucleus into the cytoplasm.
d. Nuclear pore complexes can regulate the speed at which newly synthesized proteins are exported from the nucleus into the cytoplasm.
T/F Each nucleotide in an mRNA encodes one amino acid in a protein.
False
T/F Since introns do not contain protein coding information, they do not have to be removed precisely (meaning, a nucleotide here and there should not matter) from the primary transcript during RNA splicing.
False
At which end of an mRNA molecule do ribosomal subunits first bind? a. The 3' end b. The 5' end
The 5' end
You have discovered a protein that inhibits translation. When you add this inhibitor to a mixture capable of translating human mRNA and centrifuge the mixture to separate polyribosomes and single ribosomes, you obtain the results shown in the figure below. Which of the following interpretations is consistent with these observations? a. The protein binds to the small ribosomal subunit and increases the rate of initiation of translation. b. The protein binds to sequences in the 5′ region of the mRNA and inhibits the rate of initiation of translation. c. The protein binds to the large ribosomal subunit and slows down elongation of the polypeptide chain. d. The protein binds to sequences in the 3′ region of the mRNA and prevents termination of translation.
b. The protein binds to sequences in the 5' region of the mRNA and inhibits the rate of initiation of translation.
Bacterial mRNAs: a. are translated after they are exported from the nucleus. b. are transcribed and translated simultaneously. c. must be folded into the correct three-dimensional shape before they can be translated. d. are processed in the same way as eukaryotic mRNAs.
b. are transcribed and translated simultaneously.
The piece of RNA below includes the region that codes the binding site for the initiator tRNA needed in translation. 5′-GUUUCCCGUAUACAUGCGUGCCGGGGGC-3′ Which amino acid will be on the tRNA that is the first to bind to the A-site of the ribosome? a. methionine b. arginine c. cystine d. valine
b. arginine
Where in a cell are most damaged proteins broken down? a. peroxisomes b. cytosol c. Golgi apparatus d. Endoplasmic reticulum
b. cytosol
Combinatorial control of gene expression __________________________. a. involves every gene using a different combination of transcriptional regulators for its proper expression. b. involves groups of transcriptional regulators working together to determine the expression of a gene. c. involves only the use of gene activators used together to regulate genes appropriately. d. is seen only when genes are arranged in operons.
b. involves groups of transcriptional regulators working together to determine the expression of a gene.
Which of the following statements about procaryotic mRNA molecules is false? a. A single procaryotic mRNA molecule can be translated into several proteins. b. Ribosomes must bind to the 5′ cap before initiating translation. c. mRNAs are not polyadenylated. d. Ribosomes can start translating an mRNA molecule before transcription is complete.
b. ribosomes must bind to the 5' cap before initiating translation
What is the term for an RNA molecule that possesses catalytic activity? a. enzyme b. ribozyme c. catalyst
b. ribozyme
In eucaryotes, but not in procaryotes, ribosomes find the start site of translation by ____________________________. a. binding directly to a ribosome-binding site preceding the initiation codon b. scanning along the mRNA from the 5′ end c. recognizing an AUG codon as the start of translation d. binding an initiator tRNA
b. scanning along the mRNA from the 5' end
Which part of a protein is synthesized by a ribosome first? a. the C-terminus b. the N-terminus
b. the N-terminus
Imagine that an RNA polymerase is transcribing a segment of DNA that contains the following sequence: 5′-AGTCTAGGCACTGA-3′ 3′-TCAGATCCGTGACT 5′ If the polymerase is transcribing from this segment of DNA from left to right, which strand is the template? a. the top strand is the template b. the bottoms strand is the template
b. the bottom strand is the template
The owners of a local bakery ask for your help in improving a special yeast strain they use to make bread. They would like you to help them design experiments using RNA interference to turn off genes, to allow them to test their hypothesis that certain genes are important for the good flavors found in their bread. Of the components in the following list, which is the most important to check for in this yeast strain if you'd like this project to succeed? a. the presence of foreign double-stranded RNA b. the presence of genes in the genome that code for RISC proteins c. the presence of miRNA genes in the genome d. the presence of single-stranded siRNAs within the cell
b. the presence of genes in the genome that code for RISC proteins
Which of the following does not increase the stability of eukaryotic mRNAs? a. A 5'-end cap b. A poly-A tail c. An intron
c. An intron
Which of the following pairs of codons might you expect to be read by the same tRNA as a result of wobble? a. CUU and UUU b. GAU and GAA c. CAC and CAU d. AAU and AGU
c. CAC and CAU
The MyoD transcriptional regulator is normally found in differentiating muscle cells and participates in the transcription of genes that produce muscle-specific proteins, such as those needed in contractile tissue. Amazingly, expression of MyoD in fibroblasts causes these cells derived from skin connective tissue to produce proteins normally only seen in muscles. However, some other cell types do not transcribe muscle-specific genes when MyoD is expressed in them. Which of the following statements below is the best explanation of why MyoD can cause fibroblasts to express muscle-specific genes? a. Unlike some other cell types, fibroblasts have not lost the muscle-specific genes from their genome. b. The muscle-specific genes must be in heterochromatin in fibroblasts. c. During their developmental history, fibroblasts have accumulated some transcriptional regulators in common with differentiating muscle cells. d. The presence of MyoD is sufficient to activate the transcription of muscle-specific genes in all cell types.
c. During their developmental history, fibroblasts have accumulated some transcriptional regulators in common with differentiating muscle cells.
You have discovered a gene (figure A, below) that is alternatively spliced to produce several forms of mRNA in various cell types, three of which are shown in figure B. The lines connecting the exons that are included in the mRNA indicate the splicing. From your experiments, you know that protein translation begins in exon 1. For all forms of the mRNA, the encoded protein sequence is the same in the regions of the mRNA that correspond to exons 1 and 10. Exons 2 and 3 are alternative exons used in different mRNA, as are exons 7 and 8. Which of the following statements about exons 2 and 3 is the most accurate? a. Exons 2 and 3 must have the same number of nucleotides. b. Exons 2 and 3 must contain an integral number of codons (that is, the number of nucleotides divided by 3 must be an integer). c. Exons 2 and 3 must contain a number of nucleotides that when divided by 3, leaves the same remainder (that is, 0, 1, or 2). d. Exons 2 and 3 must have different numbers of nucleotides.
c. Exons 2 and 3 must contain a number of nucleotides that when divided by 3, leaves the same remainder (that is, 0, 1, or 2).
What is the "central dogma"? a. Genetic information flows from RNA to DNA to protein. b. Genetic information flows from RNA to protein to DNA. c. Genetic information flows from DNA to RNA to protein. d. Genetic information flows from DNA to protein to RNA. e. Genetic information flows from protein to RNA to DNA. f. Genetic information flows from protein to DNA to RNA.
c. Genetic information flows from DNA to RNA to protein.
Which of the following statements about the proteasome is false? a. Ubiquitin is a small protein that is covalently attached to proteins to mark them for delivery to the proteasome. b. Proteases reside in the central cylinder of a proteasome. c. Misfolded proteins are delivered to the proteasome, where they are sequestered from the cytoplasm and can attempt to refold. d. The protein stoppers that surround the central cylinder of the proteasome use the energy from ATP hydrolysis to move proteins into the proteasome inner chamber.
c. Misfolded proteins are delivered to the proteasome, where they are sequestered from the cytoplasm and can attempt to refold.
Which of the following is well accepted in the scientific community? a. Introns evolved early in life forms, and only later did prokaryotes lose their introns. b. Introns evolved later in eucaryotes, which is why they don't appear in procaryotes. c. Neither -- the evolution of introns is still a topic of debate.
c. Neither -- the evolution of introns is still a topic of debate.
Which biochemical reaction is catalyzed by a ribozyme? a. Glycosidic bond formation in polysaccharide synthesis b. DNA polymerization during DNA replication c. Peptide bond formation in protein synthesis d. Peptide bond hydrolysis by proteases
c. Peptide bond formation in protein synthesis
Which of the following molecules is thought to have arisen first during evolution? a. protein b. DNA c. RNA d. all came to be at the same time
c. RNA
Ribozymes catalyze which of the following reactions? a. DNA synthesis b. transcription c. RNA splicing d. protein hydrolysis
c. RNA splicing
What is NOT true about codons in mRNA molecules a. Codons in mRNAs bind to complementary anticodons in tRNAs. b. Some codons do not code for amino acids. c. Some codons code for more than one amino acid. d. In some cases, several different codons code for the same amino acid.
c. Some codons code for more than one amino acid.
Which one of the following is the main reason that a typical eukaryotic gene is able to respond to a far greater variety of regulatory signals than a typical prokaryotic gene or operon? a. Eukaryotes have three types of RNA polymerase. b. Eukaryotic RNA polymerases require general transcription factors. c. The transcription of a eukaryotic gene can be influenced by proteins that bind far from the promoter. d. Procaryotic genes are packaged into nucleosomes.
c. The transcription of a eukaryotic gene can be influenced by proteins that bind far from the promoter.
Proteasomes act primarily on proteins that have been marked for destruction by the covalent attachment of which small protein? a. Protease b. Histone c. Ubiquitin d. Termination factor
c. Ubiquitin
A strain of yeast translates mRNA into protein inaccurately. Individual molecules of a particular protein isolated from this yeast have variations in the first 11 amino acids compared with the sequence of the same protein isolated from normal yeast cells, as listed in the figure below. What is the most likely cause of this variation in protein sequence? a. a mutation in the DNA coding for the protein b. a mutation in the anticodon of the isoleucine tRNA (tRNAIle) c. a mutation in the isoleucyl-tRNA synthetase that decreases its ability to distinguish between different amino acids d. a mutation in the isoleucyl-tRNA synthetase that decreases its ability to distinguish between different tRNA molecules
c. a mutation in the isoleucyl-tRNA synthetase that decreases its ability to distinguish between different amino acids.
Within the ribosome, the formation of peptide bonds is catalyzed by: a. aminoacyl-tRNA synthetase. b. the tRNA itself. c. an RNA molecule in the large ribosomal subunit. d. a peptidase in the small ribosomal subunit.
c. an RNA molecule in the large ribosomal subunit
In eukaryotes, which parts of a gene are transcribed into RNA? a. introns b. exons c. introns and exons
c. introns and exons
RNA in cells differs from DNA in that ___________________. a. it contains the base uracil, which pairs with cytosine b. it is single-stranded and cannot form base pairs c. it is single-stranded and can fold up into a variety of structures d. the sugar ribose contains fewer oxygen atoms than does deoxyribose
c. it is single-stranded and can fold up into a variety of structures
In eukaryotes, the initiator tRNA always carries which amino acid? a. glycine b. alanine c. methionine d. lysine
c. methionine
Compared to the error rate of DNA polymerase (1 error in 10^7 nucleotides), the error rate of RNA polymerase is: a. much less b. about the same c. much greater
c. much greater
Which of the following statements is true? a. Ribosomes are large RNA structures composed solely of rRNA. b. Ribosomes are synthesized entirely in the cytoplasm. c. rRNA contains the catalytic activity that joins amino acids together. d. A ribosome binds on tRNA at a time.
c. rRNA contains the catalytic activity that joins amino acids together.
You have a segment of DNA that contains the following sequence: 5′-GGACTAGACAATAGGGACCTAGAGATTCCGAAA-3′ 3′-CCTGATCTGTTATCCCTGGATCTCTAAGGCTTT-5′ If you know that the RNA transcribed from this segment contains the following sequence: 5′-GGACUAGACAAUAGGGACCUAGAGAUUCCGAAA-3′ Which of the following choices best describes how transcription occurs? a. The top strand is the template strand; RNA polymerase moves along this strand from 5′ to 3′. b. The top strand is the template strand; RNA polymerase moves along this strand from 3′ to 5′. c. The bottom strand is the template strand; RNA polymerase moves along this strand from 5′ to 3′. d. The bottom strand is the template strand; RNA polymerase moves along this strand from 3' to 5'.
d. The bottom strand is the template strand; RNA polymerase moves along this strand from 3' to 5'.
What structure is responsible for selecting and transporting only properly processed eukaryotic mRNAs into the cytoplasm? a. The spliceosome b. snRNPs c. RNA polymerase d. The nuclear pore complex e.Ribosomes
d. The nuclear pore complex
Which of the following statements is false? a. A new RNA molecule can begin to be synthesized from a gene before the previous RNA molecule's synthesis is completed. b. If two genes are to be expressed in a cell, these two genes can be transcribed with different efficiencies. c. RNA polymerase is responsible for both unwinding the DNA helix and catalyzing the formation of the phosphodiester bonds between nucleotides. d. Unlike DNA, RNA uses a uracil base and a deoxyribose sugar.
d. Unlike DNA, RNA uses a uracil base and a deoxyribose sugar.
Which of the following might decrease the transcription of only one specific gene in a bacterial cell? a. a decrease in the amount of sigma factor b. a decrease in the amount of RNA polymerase c. a mutation that introduced a stop codon into the DNA that precedes the gene's coding sequence d. a mutation that introduced extensive sequence changes into the DNA that precedes the gene's transcription start site
d. a mutation that introduced extensive sequence changes into the DNA that precedes the gene's transcription start site
Total nucleic acids are extracted from a culture of yeast cells and are then mixed with resin beads to which the polynucleotide 5′-TTTTTTTTTTTTTTTTTTTTTTTTT-3′ has been covalently attached. After a short incubation, the beads are then extracted from the mixture. When you analyze the cellular nucleic acids that have stuck to the beads, which of the following is most abundant? a. DNA b. tRNA c. rRNA d. mRNA
d. mRNA
According to current thinking, the minimum requirement for life to have originated on Earth was the formation of a _______________. a. molecule that could provide a template for the production of a complementary molecule b. double-stranded DNA helix c. molecule that could direct protein synthesis d. molecule that could catalyze its own replication
d. molecule that could catalyze its own replication
Transcription is similar to DNA replication in that ___________________. a. an RNA transcript is synthesized discontinuously and the pieces are then joined together b. it uses the same enzyme as that used to synthesize RNA primers during DNA replication c. the newly synthesized RNA remains paired to the template DNA d. nucleotide polymerization occurs only in the 5'-to-3' direction
d. nucleotide polymerization occurs only in the 5'-to-3' direction
At which site on the DNA of a gene does RNA polymerase release its newly made RNA? a. promoter b. template c. stop codon d. terminator
d. terminator
Which base is not present in RNA? a. A b. C c. G d. U e. T
e. T