Exam 3
A eukaryotic gene is observed to make multiple forms of a protein. How can one eukaryotic gene produce multiple products in the same cell? A) Alternative splicing sites can lead to the production of two different mature mRNAs from the same gene, resulting in slightly different proteins. B) Epigenetic changes can change the sequence of amino acids in a protein. C) Translation rates can affect the length of the polypeptide made from the same mRNA. D) Silencer genetic elements can cause early termination of transcription, leading to the production of multiple mature mRNAs from the same gene. E) One gene equals one protein, so this observation must be incorrect.
a
A recently isolated bacterial strain has been given to you for general characterization of the genome. You begin by isolating the DNA and subjecting it to thermal denaturation. You use Escherichia coli (E. coli) DNA as a reference. Based on the information in the graph, you can determine that the DNA of the new strain has a high a. G-C content with respect to E. coli. b. pyrimidine content with respect to E. coli. c. A-T content with respect to E. coli. d. purine content, with respect to E. coli. e. histone content with respect to E. coli.
a
After generations stemming from this individual, it must be found individual has been infected with a particular retrovirus. In order for the latent virus DNA to be inherited by subsequent A) in germ line cells. B) in stem cells. C) at a point early in childhood D) in all cells simultaneously. E) in somatic cells.
a
An elongating ribosome is bound to appropriate tRNAs in both the A and the P sites and is ready for peptidyl transfer. What happens next? A) The carboxyl end of the polypeptide chain is released from the P-site tRNA and joined to the free amino group of the amino acid linked to the A-site tRNA. B) The amino end of the polypeptide chain is released from the P-site tRNA and joined to the free carboxyl group of the amino acid linked to the A-site tRNA. C) The carboxyl end of the amino acid is released from the A-site tRNA and joined to the free amino group of the polypeptide chain linked to the P-site tRNA. D) The amino end of the amino acid is released from the A-site tRNA and joined to the free carboxyl group of the polypeptide chain linked to the P-site tRNA.
a
An elongating ribosome is bound to appropriate tRNAs in both the A and the P sites and is ready for peptidyl transfer. What happens next? a. The carboxyl end of the polypeptide chain is released from the P-site tRNA and joined to the free amino group of the amino acid linked to the A-site tRNA. b. The amino end of the polypeptide chain is released from the P-site tRNA and joined to the free carboxyl group of the amino acid linked to the A-site tRNA. c. The carboxyl end of the amino acid is released from the A-site tRNA and joined to the free amino group of the polypeptide chain linked to the P-site tRNA. d. The amino end of the amino acid is released from the A-site tRNA and joined to the free carboxyl group of the polypeptide chain linked to the P-site tRNA.
a
An enzyme that breaks DNA, dispels the tension, and reseals the strand ahead of a DNA replication growing fork is called a(n) A) topoisomerase. B) DNA polymerase. C) phosphodiesterase. D) aminoacyl-tRNA synthetase.
a
An isolate of a mutant bacterium appears to grow more slowly than the wild-type population from which it was isolated. Further studies showed that the slower growth was due to a markedly reduced DNA polymerase I activity. From this information, one would expect that this organism would also be deficient in the activity of DNA A) excision repair. B) recombination. C) transcription. D) translation. E) unwinding.
a
Approximately what percent of the human genome codes for proteins? a. 1.5% b. 10% c. 25% d. 50%
a
At the replication fork, the template for the lagging strand is thought to loop around. This looping would allow the lagging-strand polymerase to move along with the rest of the replication fork instead of in the opposite direction. The single- strand part of the loop is bound by the single-strand DNA-binding (SSB) proteins. As each Okazaki fragment is synthesized toward completion, how does the size of the loop change? What about the size of the SSB-bound part of the loop? A) Increases; increases. B) Increases; decreases. C) Decreases; increases. D) Decreases; decreases. E) Decreases; does not change.
a
DNA replication A) requires a type of RNA polymerase. B) is partially regulated by promoter/terminator sites. C) proceeds by making two continuous strands. D) is not edited once polymerization has occurred. E) is conservative.
a
Gene knockdown via RNAi relies on the ability of eukaryotic cells to A) degrade target mRNAs that are complementary to introduced dsRNA. B) induce microRNA expression under particular conditions. C) preferentially degrade mutated mRNAs. D) inhibit transcription of sets of genes based on the presence of distal control elements. E) preferentially degrade mutated mRNAs by inducing microRNA expression under particular conditions.
a
How does binding of the lac repressor to the lac operator block transcription initiation? a. lac repressor binding blocks RNA polymerase from interacting from DNA at the start site b. lac repressor binding induces a DNase that cleaves the DNA at the transcriptions tart site c. all repressor binding causes a conformation change in RNA polymerse d. lac repressor binding induces a protease that degrades the sigma subunit of RNA polymerase
a
How many protein coding genes are estimated to be in the human genome? A) 21,000 B) 35,000 C) 75,000 D) 100,000
a
How many protein coding genes are estimated to be in the human genome? A) 21,000 B) 35,000 C) 75,000 D) 100,000
a
In a double-stranded DNA molecule, one of the chains has the sequence CCCATTCTA when read from the 5′ to the 3′ end. Which is a correct statement regarding this chain. A) The other chain is heavier, i.e. it has a greater mass. B) There are no G residues in the other chain. C) The 5′-terminal residue of the other chain is G. D) The other chain is pyrimidine-rich.
a
In analysis using two-dimensional gel electrophoresis of the proteins expressed in different cell types, the number of proteins that are different in different cells usually exceeds the number of common proteins, and even the common proteins can still have different concentrations. Which of the following proteins would you expect to be among the common when compared across several cell types? A) RPL10 (a ribosomal protein) B) HBA1 (a hemoglobin subunit) C) Insulin (a hormone)
a
What would happen to the regulation of the tryptophan operon in cells that express a mutant form of the tryptophan repressor that: 1. cannot bind to DNA, 2. cannot bind tryptophan, 3. binds to DNA even in the absence of tryptophan? A) Transcription of the tryptophan operon would no longer be regulated by the absence or presence of tryptophan B) The operon would be regulated in all the scenarios. C) The enzymes would be permanently turned on in scenarios 1 and 3 and permanently shut off in scenario 2. D) The enzymes would be permanently shut off in scenarios 1 and 2 and permanently turned on in scenario 3.
a
Which of the following is a typical feature of prokaryotic genes? a. polycistronic messenger RNAs b. complex transcription units c. introns d. a and c
a
Which of the following would be most likely to accumulate changes to its sequence? a. a gene that has recently been duplicated in the genome b. a gene that codes for a highly optimized essential protein or RNA molecule c.a gene encoding DNA polymerase d. a regulatory DNA sequence e. a gene that is highly conserved among a wide diversity of organisms
a
5. All the following statements about heterochromatin are true except: A) It is a dark-staining area of a chromosome. B) It is usually transcriptionally active. C) it is often simple sequence DNA D) it is a region of condensed chromatin
b
A bacterium is suddenly expelled from a warm human intestine into the cold world outside. Which of the following adjustments might the bacterium make to maintain the same level of membrane fluidity? A) Produce lipids with hydrocarbon tails that are longer and have fewer double bonds. B) Produce lipids with hydrocarbon tails that are shorter and have more double bonds. C) Decrease the amount of cholesterol in the membrane. D) Decrease the amount of glycolipids in the membrane.
b
A drug 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
A mutation that changes the recognition sequence for the restriction enzyme EcoRI from GAATTC to GATTTC is an example of a A) single nucleotide polymorphism (SNP). B) simple sequence repeat (SSR). C) destroys the target protein D) all the above
b
Alteration of histones by addition of methyl and acetyl groups to particular amino acids A) changes B-DNA to Z-DNA. B) results in the remodeling of chromatin that can activate or inhibit gene expression. C) creates G bands seen after Giemsa staining of chromosomes. D) helps preserve telomeres during DNA replication. E) alters the denaturation and renaturation of DNA.
b
If you were designing a method to specifically inhibit prokaryotic transcription, but not eukaryotic transcription, interfering with which of the following would work best? A) activity of methyltransferases B) recognition of the prokaryotic promoter by RNA polymerase C) DNase activity D) RNA polymerase II activity E) ribosomal binding to mRNA
b
In RNA interference studies, the double-stranded RNA A) disrupts the target DNA sequence. B) results in the destruction of the target mRNA. C) destroys the target protein D) all of the above
b
It has been shown that inhibition of a key chromatin remodeling complex known as NuRD, by deleting one of its subunits can result in a significant increase in the efficiency of reprogramming of somatic cells into pluripotent stem cells. The reprogramming is normally done by the induced expression of a batter of transcription factors in the somatic cells, but is typically not very efficient. Such an observation suggests that the NuRD complex is normally involved in a. erasing the epigenetic memory in somatic cells b. maintaining the epigenetic memory in somatic cells c. preventing DNA replication d. formation of extended loops from chromosome territories
b
It has been shown that inhibition of a key chromatin remodeling complex known as NuRD, by deleting one of its subunits, can result in a significant increase in the efficiency of reprogramming of somatic cells into pluripotent stem cells. The reprogramming is normally done by the induced expression of a battery of transcription factors in the somatic cells, but is typically not very efficient. Such an observation suggests that the NuRD complex is normally involved in ... A) erasing the epigenetic memory in somatic cells. B) maintaining the epigenetic memory in somatic cells. C) preventing DNA replication. D) formation of extended loops from chromosome territories.
b
Nonhomologous end joining is used to A) correct base mismatches in newly synthesized DNA. B) fix double-strand DNA breaks. C) avoid deletion or insertion of bases. D) remove modified or depurinated bases.
b
Nonhomologous end joining is used to A) correct base mismatches in newly synthesized DNA. B) fix double-strand DNA breaks. C) avoid deletion or insertion of bases. D) remove modified or depurinated bases. E) avoid deletion or insertion of bases and remove modified or depurinated bases.
b
On the ribosome, the mRNA is read from ..., and the polypeptide chain is synthesized from a. 5' to 3'; C- to N-terminus. b. 5' to 3'; N- to C-terminus. c. 3' to 5'; C- to N-terminus. d. 3' to 5'; N- to C-terminus.
b
Protein subunits that interact specifically with DNA sequences a. typically recognize sequences of two to three nucleotide pairs in length. b. do so via hydrogen bonds, ionic bonds, and hydrophobic interactions. c. typically form about five weak interactions at the protein-DNA interface. d. often bind loosely to DNA. e. All of the above.
b
Regulation of transcription by steroid hormones A) involves hormone receptors normally found in the nucleus. B) involves cytoplasmic hormone receptors that can move to the nucleus. C) involves two ligase domains. D) always activates transcription.
b
You are studying a eukaryotic gene whose initial transcript is 1500 nucleotides in length. The mature mRNA derived from the gene is 1200 nucleotides in length. What is the most probable reason for the discrepancy? A) a mutation that results in a shorter product B) removal of introns C) removal of exons D) mRNA breakage E) A mutation that results in a shorter product or mRNA breakage could have occurred
b
Researchers often want to isolate a certain type of RNA. For some RNA species, this can be accomplished via affinity chromatography, using beads coated with chains of poly-deoxythymidine (poly-dT). The desired RNA will stick to the beads while unwanted RNAs will flow through the column. The retained RNA can then be eluted. What RNA species can be purified using this method? a. eukaryotic rRNA b. bacterial rRNA c. eukaryotic mRNA d. bacterial mRNA
c
Short micro RNAs (miRNAs) a. code for proteins b. are common in bacteria but not eukaryotes c. are involved in regulation of gene expression d. have no known function
c
Since cancer is caused by mutations in genes, most mutagens are considered carcinogenic compounds. Thus, a simple test to see whether or not a compound is mutagenic is highly useful. A variation on the mutation rate assay shown below provides a simple assessment of the mutagenic ability of agents. In this variation, two histidine-requiring E. coli cultures are grown in parallel. Both are inoculated into histidine-containing medium. Culture B medium also contains a potential mutagenic agent, while culture A does not. Later, each culture is spread on its own plate on a medium lacking histidine, and cells that can produce their own histidine grow into visible colonies. If culture B is exposed to a mutagen, what is the expected result? a. Culture B will have fewer colonies on the histidine-minus plate than culture A. b. Culture B will not have any colonies at all due to the detrimental nature of mutagens. c. Culture B will have more colonies on the histidine-minus plate than culture A. d. Culture B will have the same number of colonies as culture A.
c
Splice sites in pre-mRNA are marked by two universally conserved sequences contained A) in the middle of the intron. B) at the ends of the exons. C) at the ends of the introns. D) none of the above
c
The position effect variegation (PEV) phenotype described in this chapter can be only used to identify new genes that regulate heterochromatin formation. For instance, strains of Drosophila melanogaster with the White variegation phenotype have been subjected to mutagenesis to screen for dominant mutations (in other genes) that either enhance or suppress PEV, meaning the mutations result in either lower or higher red pigment production, respectively. Which of the following mutations is expected to be an enhanced of variegation? a. a mutation that results in the loss of function of the fly's HP1 (heterochromatin protein 1) gene b. a loss-of-function mutation in a gene encoding a histone deacetylase that deacetylates lysine 9 on histone H3 c. A gain-of-function mutation in a gene encoding a histone methyl transferase that trimethylates lysine 9 on histone H3, resulting in a hyperactive form of the enzyme d. a gain-of-function mutation in a gene encoding a histone acetyl transferase that normally acetylates lysine 9 on histone H3, resulting in higher expression of the protein
c
Three phospholipids, X, Y, and Z are distributed in the plasma membrane as indicated in the figure. For which of these phospholipids does a flippase probably exist? a. X only b. Z only c. X and Y d. Y and Z
c
What characteristic is shared between most prokaryotic and mitochondrial genomes? A) <5 % protein-coding genes B) >20% interspersed repeats C) circular chromosomes D) linear chromosomes E) circular chromosomes with <5 % protein-coding genes
c
What is the main source of the free energy for the mechanical work performed by DNA helicases during DNA replication in our cells? A) The hydrogen-bonding energy in the DNA double helix B) Thermal energy in the nucleus C) ATP hydrolysis by the helicase D) The energy of SSB binding to single-stranded DNA E) ATP hydrolysis by DNA topoisomerases
c
What is the main source of the free energy for the mechanical work performed by DNA helicases during DNA replication in our cells? a. The hydrogen-bonding energy in the DNA double helix b. Thermal energy in the nucleus c. ATP hydrolysis by the helicase d. The energy of SSB binding to single-stranded DNA e. ATP hydrolysis by DNA topoisomerases
c
Which of the following enzymes is associated with the formation of peptide bonds? a. peptidase b. aminoacyl transferase c. peptidyl transferse d. peptide hydrolase e. DNA polymerase
c
Which of the following enzymes will produce a blunt end (the cut site is indicated by the * in the recognition sequence)? A) TaqI (T*CGA) B) EagI (C*GGCCG) C) EcoRV (GAT*ATC) D) NsiI (ATGCA*T)
c
Which of the following features is common between the replication origins in Escherichia coli and Saccharomyces cerevisiae? A) They both normally exist in one copy per genome. B) Both are specified by DNA sequences of tens of thousands of nucleotide pairs. C) Both contain sequences that attract initiator proteins, as well as stretches of DNA rich in A-T base pairs. D) Both contain GATC repeats that are methylated to prevent the inappropriate "firing" of the origin. E) All of the above.
c
Which of the following features is common between the replication origins in Escherichia coli and Saccharomyces cerevisiae? a. They both normally exist in one copy per genome. b. Both are specified by DNA sequences of tens of thousands of nucleotide pairs. c. Both contain sequences that attract initiator proteins, as well as stretches of DNA rich in A-T base pairs. d. Both contain GATC repeats that are methylated to prevent the inappropriate "firing" of the origin. e. All of the above.
c
Which of the following features of DNA underlies its simple replication procedure? A) The fact that it is composed of only four different types of bases B) The antiparallel arrangement of the double helix C) The complementary relationship in the double helix D) The fact that there is a major groove and a minor groove in the double helix
c
Which 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. prokaryotic genes are packaged into nucleosomes
c
Which of the following modifications to histone H3 promote gene silencing? a. acetylation and methylation b. acetylation and demethylation c. deacetylation and methylation d. deacetylation and demethylation
c
Which of the following statements is not true about the differences between liver cells and kidney cells in the same organism? a. They express different genes. b. They contain the entire set of instructions needed to form the whole organism. c. They contain different genes. d. They contain different proteins.
c
Which type of DNA makes up the smallest portion of the human genome? A) introns B) unique noncoding DNA C) exons D) tandemly repeated DNA E) interspersed repeated DNA
c
In DNA replication, the leading strand of DNA ________, while the other newly forming strand, called the lagging strand, ________. A) is synthesized in the 5' → 3' direction; the new DNA is synthesized in the 3' → 5' direction B) is synthesized in the 3' → 5' direction; the new DNA is synthesized in the 5' → 3' direction C) does not require an RNA primer; an RNA primer is required D) is synthesized as a continuous chain; the new DNA is formed in a series of short, discontinuous fragments E) is synthesized in a series of short, discontinuous fragments; the new DNA is synthesized as a continuous chain
d
In the following schematic graph of a hypothetical set of RNA-seq data, the number of reads is plotted for a region of chromosome containing two genes, from samples obtained from two different tissues. Which gene (X or Y) do you think is more likely a "housekeeping" gene? Which region (1 or 2) within gene Y most likely corresponds to an exon? a. Gene X; region 1 b. Gene X, region 2 c. both genes, region 1 d. Gene Y, region 1 e. Gene Y, region 2
d
Mismatch repair targets improperly paired nucleotides. In prokaryotes, the incorrect member of an abnormal base pair can be differentiated from the correct member because A) the incorrect member has undergone a hydroxylation reaction. B) newly synthesized DNA contains uracil. C) the incorrect member doesn't match the surrounding bases. D) the original strand of DNA contains methylated bases while newly synthesized DNA does not; thus the correct member is in the methylated strand. E) the correct member has been deaminated.
d
Mismatch repair targets improperly paired nucleotides. The incorrect member of an abnormal base pair can be differentiated from the correct member because A) the incorrect member has undergone a hydroxylation reaction. B) newly synthesized DNA contains uracil. C) the incorrect member doesn't match the surrounding bases. D) the original strand of DNA contains methylated bases while newly synthesized DNA does not; thus the correct member is in the methylated strand. E) the correct member has been deaminated.
d
Mobile DNA elements likely contributed to the evolution of higher organisms by the a. generation of gene families by gene duplication b. creation of new genes by exon shuffling c. formation of more complex regulatory regions d. all of the above
d
On average, errors occur in DNA synthesis only once in every ten billion nucleotides incorporated. Which of the following does NOT contribute to this high fidelity of DNA synthesis? A) Complementary base-pairing between the nucleotides B) Exonucleolytic proofreading by the 3′-to-5′ exonuclease activity of the enzyme to correct mispairing even after monomer incorporation C) A strand-directed mismatch repair system that detects and resolves mismatches soon after DNA replication D) All of the above mechanisms DO contribute to the fidelity.
d
On average, errors occur in DNA synthesis only once in every ten billion nucleotides incorporated. Which of the following does NOT contribute to this high fidelity of DNA synthesis? a. Complementary base-pairing between the nucleotides b. Exonucleolytic proofreading by the 3′-to-5′ exonuclease activity of the enzyme to correct mispairing even after monomer incorporation c. A strand-directed mismatch repair system that detects and resolves mismatches soon after DNA replication d. All of the above mechanisms DO contribute to the fidelity.
d
Telomeres serve as caps at the ends of linear chromosomes. Which of the following is not true regarding the replication of telomeric sequences? a. The lagging-strand telomeres are not completely replicated by DNA polymerase. b. Telomeres are made of repeating sequences. c. Additional repeated sequences are added to the template strand. d. The leading strand doubles back on itself to form a primer for the lagging strand.
d
The 5' end of a DNA molecule can be chemically distinguished from the 3' end because there is a(n) ________ group at the 5' end and a(n) ________ group at the 3' end. A) amine; carboxyl B) phosphate; sulfate C) hydroxyl; hydrogen D) phosphate; hydroxyl E) amine; hydroxyl
d
The TATA box A) serves as a promoter sequence for genes transcribed by RNA polymerase III. B) is located approximately 100 base pairs upstream of the start site for mRNAs. C) is present in all eukaryotic genes. D) acts to position RNA polymerase II for transcription initiation.
d
The accompanying graph shows a growth curve of E. coli growing in a defined medium containing equal molar amounts of glucose and lactose. Based on your knowledge of the regulation of the lac operon, the best explanation of these results is that A) early on, due to the presence of lactose, the bacteria use the lac operon. Glucose is used later. B) the bacteria use both sugars simultaneously. C) the presence of glucose causes the formation of cAMP catabolite activator protein (CAP) complexes, which shut down the lac operon until the glucose is used up. D) glucose is used first. Once glucose becomes limiting, intracellular cAMP increases, forming cAMP-CAP complexes that activate the lac operon to use lactose. E) early on the glucose binds to the repressor protein lacl and shuts down the lac operon
d
The figure shows the evolutionary history of the globin gene family members. Given this information, which of the following statements is true? A) The ancestral globin gene arose 500 million years ago. B) The α-globin gene is more closely related to the ε-globin gene than to the δ-globin gene. C) The nucleotide sequences of the two γ-globins will be most similar because they are the closest together on the chromosome. D) The fetal β-globins arose from a gene duplication that occurred 200 million years ago, which gave rise to a β-globin expressed in the fetus and a β-globin expressed in the adult.
d
The normal gene for hemoglobin was isolated, cloned in E. coli, and subjected to restriction enzyme digestion with BamHI. Following gel electrophoresis, three bands are routinely obtained. However, following the same procedure with the hemoglobin gene from an individual with sickle cell anemia, four bands are routinely obtained. These data suggest that A) the mutation associated with sickle cell anemia results in DNA that breaks easily. B) the mutation associated with sickle cell anemia results in the loss of a BamHI cut site. C) the mutation associated with sickle cell anemia results in several new enzyme cut sites for a variety of restriction enzymes. D) the mutation associated with sickle cell anemia results in the gain of a BamHI cut site. E) the assay was not performed correctly.
d
When comparing different species, which of the following best predict the relative number of genes in each species? a. the complexity of the organism b. the size of the organism c. the size of its brain d. the size of the genome e. the number of chromosomes
d
Which of the following is a protein that is involved in translation? A) topoisomerase B) ribosomal RNA C) RNA polymerase D) aminoacyl-tRNA synthetase
d
Which of the following is not a structural motif found in a DNA-binding domain? A) homeodomain B) zinc-finger C) helix-loop-helix D) random-coil acidic domain
d
Which of the following is not associated with mRNA processing in eukaryotes? A) addition of a 5' methyl guanosine cap B) 3' polyadenylation C) removal of introns D) removal of exons E) removal of exons and introns
d
Which of the following is true regarding heterochromatin in a typical mammalian cell? a. about 1% of the nuclear genome is packaged in heterochromatin b. the DNA in heterochromatin contains all of the inactive genes in a cell c. genes that are packaged in heterochromatin are permanently turned off d. the different types of heterochromatin share an especially high degree of compaction e. heterochromatin is highly concentrated in the centromeres but not the telomeres
d
Which of the following methods is not used by cells to regulate the amount of protein in a 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
Which of the following repair pathways can accurately repair a double-strand break? a. Base excision repair b. Nucleotide excision repair c. Direct chemical reversal d. Homologous recombination e. Nonhomologous end joining
d
Which of the following structures interacts with ribosomes? a. tRNA b. mRNA c. rRNA d. all of the above
d
You have discovered an "Exo-" mutant form of DNA polymerase in which the 3'-5' exonuclease function has been destroyed but the ability to join nucleotides together is unchanged. Which of the following properties do you expect the mutant polymerase to have? a. it will polymerize in both the 5'-3' direction and the 3'-5' direction b. it will polymerize more slowly than the normal Exo+ polymerase c. it will fall off the template more frequently than the normal Exo+ polymerase d. it will be more likely to generate mismatched base pairs
d
You have isolated a piece of DNA that you believe contains an interesting gene. Using a mix of RNA polymerase and ribonucleotides, you perform in vitro transcription. However, even though all of your controls work, no mRNA is created from your DNA fragment. Working backward, you note that your DNA preparation removed approximately 250 base pairs from the 5' end of the gene. The most likely explanation is that during DNA preparation A) the termination signal was removed. B) the RNA polymerase became inactivated. C) the 5' methyl guanosine cap was removed. D) the promoter was removed. E) None of these explains the negative results.
d
Compared to the human genome, the genome of yeast typically has a. more repetitive DNA b. longer genes c. more introns d. longer chromosomes e. a higher fraction of coding DNA
e
Compared to the human genome, the genome of yeast typically has... a. more repetitive DNA b. longer genes c. more introns d. longer chromosomes e. a higher fraction of coding DNA
e
Consider the following image of multiple genes (a and b) on a chromosome . Based on the figure, which of these statements is/are correct? a. For different genes, opposite strands of DNA can serve as a template. b. The template strand is always read by RNA polymerase in the 5'-to-3' direction. c. RNA is always polymerized in the 5'-to-3' direction. d. The gene promoter is always downstream of the transcription start site. e. Both A and C
e
FRAP has revealed that some proteins move in cell membranes much slower than they move in reconstituted liposomes. Which of the following could account for limited mobility of proteins in cell plasma membranes? A) association with other proteins in a large complex. B) association with lipid rafts. C) anchorage to the extracellular matrix. D) anchorage to the cell cytoskeleton. E) All could limit protein mobility.
e
Long interspersed nuclear elements (LINEs) found in eukaryotic genomes A) are mobile pieces of DNA called transposons that can copy themselves and move around the genome. B) are thought to create genomic variability important to evolutionary adaptation. C) are repeated 10-1000 times in clusters near centromeres and telomeres. D) are part of constitutive heterochromatin. E) are mobile pieces of DNA called transposons that can copy themselves and move around the genome, and they are thought to create genomic variability important to evolutionary adaptation.
e
Most fish genomes are at least 1 billion nucleotide pairs long. However, the genome of the puffer fish Fugu rubrics is quite small at only about 0.4 billion nucleotide pairs, even though the number of Fugu genes is estimated to be comparable to that of its relatives which have larger genomes. What do you think mainly accounts for the Fugu genome being this small? a. evolutionary advantage of extremely small exon sizes in the Fugu lineage b. unusual disappearance of all intronic sequences from the Fugu genome c. increased abundance of transposable elements in the Fugu genome d. increased occurrence of mitotic whole-chromosome loss in the Fugu lineage e. low relative rate of DNA addition compared to DNA loss in the Fugu lineage
e
The action of a new drug is unknown, so you test various aspects of eukaryotic cell processes looking for an effect. You notice that the survival of cells exposed to this drug is very low. Further analysis shows that some proteins and mRNAs are much longer than they should be. One hypothesis is that the drug interferes with A) transcription termination signals. B) spliceosome activity. C) ribosomes. D) nucleoli. E) either transcription termination signals or spliceosome activity.
e
The globing gene family in mammals, birds, and reptiles is organized into alpha and beta globin gene clusters that are located on two different chromosomes. In most fish and amphibians, however, the globin genes are close to each other on one chromosome. At which point (A to E) in the following simplified phylogenetic tree is a chromosomal translocation likely to have happened that - -globin genes on two separate chromosomes?What determines the time and place that a certain gene is transcribed in the cell? A) The type of regulatory sequences associated with it B) The relative position of regulatory sequences associated with it C) The arrangement of various regulatory sequences associated with it D) The specific combination of transcription regulators present in the nucleus E) All of the above
e
The nuclear DNA polymerases in human cells a. polymerize about 1000 nucleotides per second during DNA replication in vivo. b. are incapable of 3′-to-5′ exonuclease activity. c. are capable of 3′-to-5′ DNA polymerase activity. d. have a single active site that is used for both polymerization and editing. e. are unable to initiate polymerization de novo (i.e. in the absence of a primer).
e
The nuclear DNA polymerases in human cells ... A) polymerize about 1000 nucleotides per second during DNA replication in vivo. B) are incapable of 3′-to-5′ exonuclease activity. C) are capable of 3′-to-5′ DNA polymerase activity. D) have a single active site that is used for both polymerization and editing. E) are unable to initiate polymerization de novo (i.e. in the absence of a primer).
e
Upon binding the short complementary RNA as shown, the target RNA will be a. capped b. degraded c. exported d. translated e. none of the above
e
Which of the following statements is supported by the information in this image and is consistent with your knowledge regarding genomic architecture in prokaryotes and eukaryotes? a. The prokaryotic cell must have a nuclear spliceosome to remove introns from DNA. b. The eukaryotic cell must have a nuclear spliceosome to remove introns from DNA. c. The prokaryotic cell must have a cytoplasmic spliceosome to remove introns from RNA. d. The eukaryotic cell must have a cytoplasmic spliceosome to remove introns from RNA. e. The eukaryotic cell must have a nuclear spliceosome to remove introns from RNA.
e
Many antibiotics work by inhibiting bacterial protein synthesis. Investigators have isolated a promising new compound and wish to determine its mechanism of action. Using a cell-free translation system similar to the ones originally used to deduce the genetic code, the researchers incubate their drug with the synthetic polynucleotide 5'-AUGUUUUUUUUU. In the absence of the drug, this polynucleotide directs the synthesis of the peptide Met-Phe-Phe-Phe. When the drug is added, only the peptide Met-Phe is produced. Based on this observation, which is most likely the mechanism of action of this potential new antibiotic? a. It blocks translocation of the large ribosomal subunit, preventing the movement of peptidyl-tRNA from the A site to the P site of the ribosome. b. It inhibits the peptidyl transferase activity of the large ribosomal subunit. c. It blocks binding of aminoacyl-tRNA to the A site of the ribosome. d. It inhibits peptide bond formation.
a
Of the following steps associated with translation, which does not involve hydrolysis of GTP? A) aminoacylation of tRNA B) formation of the initiation complex C) binding of the aminoacyl tRNA to the codon at the A site D) translocation of the ribosome E) release of polypeptide
a
RNA editing is A) post-transcriptional alteration of sequences in mRNAs. B) pretranscriptional alteration of sequences in RNAs. C) post-transcriptional joining of two RNA molecules. D) none of the above
a
Researchers assayed the activity of enzyme F in three different types of tissue from the same mouse by determining the amount of enzyme product produced per milligram of tissue per unit time. As shown in the graph below, results indicate more product generation in the liver compared to the kidney and muscle samples. Which of the following factors would not explain the different results among the three tissues? a. differences in the DNA content among the tissue types b. differences in the transcription of the gene encoding the enzyme among the tissue types c. differences in the post-translational modifications of the enzyme among the tissue types d. differences in the translation of the mRNA encoding the protein among the tissue types
a
The DNA polymerase reaction occurs in the ________ as incoming nucleotides are added to ________ end(s) of the growing DNA chain. A) 5' → 3' direction; the 3'-hydroxyl B) 5' → 3' direction; the 3'-phosphate E) 5' → 3' direction or 3' → 5' direction; both C) 3' → 5' direction; the 5'-hydroxyl D) 3' → 5' direction; the 5'-phosphate
a
The Trp operon in Escherichia coli encodes the components necessary for tryptophan biosynthesis. In the presence of the amino acid in a bacterium a. the tryptophan repressor is bound to the tryptophan operator. b. the tryptophan repressor is bound to bacterial RNA polymerase. c. the expression of the tryptophan repressor is shut off. d. the operon genes are expressed. e. All of the above.
a
The Trp operon in Escherichia coli encodes the components necessary for tryptophan biosynthesis. In the presence of the amino acid in a bacterium, A) the tryptophan operator is bound to the tryptophan repressor. B) the tryptophan repressor is bound to bacterial RNA polymerase. C) the expression of the tryptophan repressor is shut off. D) the operon genes are expressed. E) All of the above.
a
The composition of lipids in the outer and inner monolayers of cell membrane lipid bilayers is A) asymmetrical; i.e., different in each monolayer. B) identical in each monolayer. C) twice as concentrated in the inner monolayer as in the outer monolayer. D) highly random for each monolayer. E) the same for all cell plasma membranes but different from the composition in mitochondrial and chloroplast membranes.
a
The eukaryotic chromosomes are organized inside the nucleus with a huge compaction ratio of several-thousand-fold. What is responsible for such a tight packaging? A) The various chromatin proteins that wrap and fold the DNA B) The nuclear envelope which encapsulates the chromosomes C) The nuclear matrix that provides a firm scaffold D) All of the above
a
The genetic information carried by a cell is passed on, generation after generation, with astonishing fidelity. However, genomes are still altered over evolutionary time scales, and even their overall size can change significantly. Which of the following genome-altering events has increased the size of the mammalian genome the most? A) Transposition B) Point mutation C) Chromosomal deletion D) Chromosomal inversion E) Chromosomal translocation
a
The genetic information carried by a cell is passed on, generation after generation, with astonishing fidelity. However, genomes are still altered over evolutionary time scales, and even their overall size can change significantly. Which of the following genome-altering events has increased the size of the mammalian genome the most? a. transposition b. point mutation c. chromosomal deletion d. chromosomal inversion e. chromosomal translocation
a
The telomerase enzyme in human cells a. has an RNA component. b. extends the telomeres by its RNA polymerase activity. c. polymerizes the telomeric DNA sequences without using any template. d. removes telomeric DNA from the ends of the chromosomes. e. creates the "end-replication" problem.
a
The telomerase enzyme in human cells ... A) has an RNA component. B) extends the telomeres by its RNA polymerase activity. C) polymerizes the telomeric DNA sequences without using any template. D) removes telomeric DNA from the ends of the chromosomes. E) creates the "end-replication" problem.
a
Thymine is used in DNA despite the fact that it is energetically more expensive to synthesize than uracil because A) spontaneous deamination reactions convert cytosine to uracil at a fairly high rate. B) uracil is more sensitive to ultraviolet (UV) damage. C) uracil is more susceptible to depurination. D) uracil can only bind with ribose, not deoxyribose. E) thymine is less likely to undergo spontaneous deamination than uracil.
a
Smilin is a hypothetical protein that causes people to smile more often. It is inactive in many chronically unhappy people. The mRNA isolated from a number of different unhappy persons in the same family is found to lack an internal stretch of 173 nucleotides that is present in the smilin mRNA isolated from a control group of happy people. The DNA sequences of the smilin genes from the happy and the unhappy families were determined and compared. They differed by a single nucleotide substitution, which lay in an intron. What is a possible molecular mechanism by which a single nucleotide substitution in a gene could cause the observed deletion in the mRNA? A) A nonsense mutation in the middle of intron 1 B) A mutation in the 3′ splice site of intron 1 C) A mutation in the 5′ splice site of intron 1 D) A mutation in the 3′ splice site of intron 2 E) A mutation in the 5′ splice site of intron 2
b
Studying the expression of a transcription regulatory protein in two cell types, you have performed experiments showing that the mRNA encoding the protein is present at comparable levels in the cytosol of both cell types. However, based on the expression of its target genes, you suspect that the protein activity might be significantly different in the two cell types. Which of the following steps in expression of the gene encoding this protein is more likely to be differentially controlled in these cell types? A) Transcription B) Translation C) mRNA transport D) mRNA degradation
b
Studying the expression of a transcription regulatory protein in two cell types, you have performed experiments showing that the mRNA encoding the protein is present at comparable levels in the cytosol of both cell types. However, based on the expression of its target genes, you suspect that the protein activity might be significantly different in the two cell types. Which of the following steps in expression of the gene encoding this protein is more likely to be differentially controlled in these cell types? a. Transcription b. Translation c. mRNA transport d. mRNA degradation
b
The base composition in DNA isolated from cow liver cells is 28% adenine; what percent of the bases are cytosine? A) 14% B) 22% C) 28% D) 36% E) 56%
b
The copy number of some human genes, such as the salivary amylase gene AMY1, varies greatly between different individuals. The salivary amylase breaks down some of the dietary starch into smaller sugars. In the case of AMY1, a positive correlation has been observed between the copy number and the amount of amylase in the saliva. Gene copy number per diploid genome can be estimated by performing a quantitative polymerase chain reaction (PCR) using primers specific to the gene of interest. You have performed such PCR experiments on samples from two human populations that have traditional diets with low and high starch levels, respectively, and have plotted the data in the histogram below. Which population (A or B) in the histogram is likely to be the one with traditionally higher dietary starch? a. population A b. population B
b
The sequence of the coding strand of a DNA molecule (that is, the DNA strand that contains the codons specifying the protein sequence) is 5'-CGGATGCTTA-3'. What is the sequence of the RNA made from this DNA? a. 5'-UAAGCAUCCG-3' b. 5'-CGGAUGCUUA-3' c. 5'-AUUCGUAGGC-3' d 5'-TAAGCATCCG-3' e. 5'-GCCUACGAAU-3'
b
Three phospholipids, X, Y, and Z are distributed in the plasma membrane as indicated in the figure. For which of these phospholipids does a flippase probably NOT exist? a. X only b. Z only c. X and Y d. Y and Z
b
To crack the genetic code, researchers introduced synthetic messenger RNAs into in vitro translation systems and determined which proteins were produced from these synthetic mRNAs. mRNAs consisting of poly-UUC led to production of three different proteins: poly-Phe, poly-Ser, and poly-Leu. What best explains this result? a. Each amino acid is specified by several codons. b. Transcription started at three different places. c. The synthetic mRNA was read in all three reading frames. d. Each codon codes for several different amino acids.
b
Transcription regulation has similarities and differences in bacteria and in eukaryotes. Which of the following is correct in this regard? A) Most bacterial genes are regulated individually, whereas most eukaryotic genes are regulated in clusters. B) The rate of transcription for a eukaryotic gene can vary in a much wider range than for a bacterial gene (which is, at most, only about 1000-fold). C) DNA looping for gene regulation is the rule in bacteria but the exception in eukaryotes. D) Transcription regulators in both bacteria and eukaryotes usually bind directly to RNA polymerase. E) The default state of both bacterial and eukaryotic genomes is transcriptionally active.
b
Transepithelial glucose transport uses a symport to transport glucose up a concentration gradient by a. coupling glucose transport to proton movement b. coupling glucose transport to Na+ movement c. coupling glucose transport to Ca2+ movement d. coupling glucose transport to Cl- movement
b
Under which of the following conditions is the Lac operon in Escherichia coli fully turned on? A) Low glucose and lactose levels B) Low glucose but high lactose levels C) High glucose but low lactose levels D) High glucose and lactose levels E) Low cAMP and high glucose levels
b
Under which of the following conditions is the Lac operon in Escherichia coli fully turned on? a. Low glucose and lactose levels b. Low glucose but high lactose levels c. High glucose but low lactose levels d. High glucose and lactose levels e. Low cAMP and high glucose levels
b
Unusual eukaryotic-like (possessing a defined nucleus) cells were obtained from a sample of water from a subglacial Antarctic lake. To investigate the properties of the new organism's genome, the nucleus was carefully isolated and the chromatin obtained. The fibers had a "beads on a string" appearance, suggesting some type of "histones." Following digestion with micrococcal nuclease, protein removal, and gel electrophoresis, DNA fragments were obtained that are multiples of 280 base pairs in length. Longer incubation with micrococcal nuclease prior to protein removal results in fragments 200 base pairs in length. The amount of DNA that is wrapped around the "core histones" is therefore A) 80 base pairs in length. B) 200 base pairs in length. C) 360 base pairs in length. D) 480 base pairs in length.E) Not enough information is given to determine the answer.
b
Which of the following describes the Lac operon in E. coli when lactose, but not glucose, is present in the culture medium? a. Neither CAP nor the Lac repressor is bound to the Lac operon's regulatory DNA, and the Lac operon is not expressed. b. CAP, but not the Lac repressor, is bound to the Lac operon's regulatory DNA, and the Lac operon is expressed. c. The Lac repressor, but not CAP, is bound to the Lac operon's regulatory DNA, and the Lac operon is not expressed. d. Neither CAP nor the Lac repressor is bound to the Lac operon's regulatory DNA, and the Lac operon is expressed. e. CAP and the Lac repressor are both bound to the Lac operon's regulatory DNA, and the Lac operon is not expressed.
b
Which of the following is a fundamental difference between gene regulation in bacteria compared to eukaryotes? A) In bacteria, but not eukaryotes, there is a specific sequence that specifies where RNA polymerase binds and initiates transcription. B) In eukaryotes, but not bacteria, transcription can be influenced by how effectively the DNA sequence of a promoter region interacts with histone octomers. C) Transcription regulation is the most widespread form of control of gene expression in bacteria but not in eukaryotes. D) Gene regulation is readily reversible in eukaryotes but not bacteria.
b
Which of the following is a fundamental difference between gene regulation in bacteria compared to eukaryotes? a. in bacteria, but not eukaryotes, there is a specific sequence that specifies where RNA polymerase binds and initiates transcription b. in eukaryotes, but not bacteria, transcription can be influenced by how effectively the DNA sequence of a promoter region interacts with histone octomers c. transcription regulation is the most widespread form of control of gene expression in bacteria but not in eukaryotes d. gene regulation is readily reversible in eukaryotes but not bacteria
b
Which of the following is correct regarding the mutation rate of genomic DNA in different organisms? a. Human cells have a much higher mutation rate compared to bacteria when the rate is normalized to a single round of replication over the same length of DNA. b. Mutation rates limit the number of essential genes in an organism's genome. c. Mutations in the somatic cells cannot be lethal. d. Even if the mutation rate was 10 times higher than its current value, germ-cell stability in humans would not have been affected. e. All of the above.
b
Which of the following is not a reason for the importance of mRNA processing in eukaryotes? A) longevity in the cytoplasm B) coupling of transcription and translation C) presence of a nuclear membrane D) turnover in the cytoplasm E) removal of introns
b
Which of the following occur without coupling transport of the solute to the movement of a second solute? a. import of glucose into the cut b. export of Ca2+ from the cytosol c. export of H+ from animal cells for pH regulation d. the export of Na+ from cells to maintain resting membrane potential
b
Which of the following statements is correct regarding ATP driven pumps>? a. ATP driven pumps have ion selectivity filters b. Eukaryotic cells contain a variety of ATP driven pumps including Na+/K+ ATPase, Ca++ ATPase and H+ ATPase c. All ATP driven pumps are found in the plasma membrane d. Inhibition of the Na+/K+ ATPase would result in [K+in]>[K+out]
b
Which of the following would most reliably suggest that a genomic sequence is functionally important? a. The presence of a long open reading frame in the sequence b. Multispecies conservation of the sequence c. Low copy number variation of the sequence d. The presence of active chromatin marks over the sequence
b
Which strand is the coding strand (not the template strand), and where is the N-terminal end of the resulting peptide located? (Hint: AUG is the start codon) a. the top strand is the coding strand, and the N-terminus is on the right b. the top strand is the coding strand, and the N-terminus is on the left c. the bottom strand is the coding strand, and the N-terminus is on the right d. the bottom strand is the coding strand, and the N-terminus is on the left e. not enough information is given to answer this question
b
You have engineered the X chromosomes in female mice such that one X chromosome expresses green fluorescent protein when active, while the other expresses red fluorescent protein. You have used these mice to study cancer in females. You know that each tumor is a clonal cellular proliferation, meaning all of its proliferating cells are descendants of a single original cancer- causing cell. It follows that, unless X-chromosome inactivation is perturbed in tumors, A) all tumor cells in one mouse should express the same fluorescent protein (either red or green), but tumor cells from different mice can show either red or green fluorescence. B) the cells in any tumor should all express the same fluorescent protein (either red or green), but independently derived tumors in the same mouse can show either green or red fluorescence. C) different cells within each tumor can express different fluorescent proteins, and the tumors would therefore show yellow fluorescence, but each cell shows either red or green fluorescence. D) each cell can express both fluorescent proteins and would therefore emit yellow fluorescence, and the tumors would glow in yellow as well. E) different tumors would show red, yellow, or green fluorescence.
b
You have engineered the X chromosomes in female mice such that one X chromosome expresses green fluorescent protein when active, while the other expresses red fluorescent protein. You have used these mice to study cancer in females. You know that each tumor is a clonal cellular proliferation, meaning all of its proliferating cells are descendants of a single original cancer-causing cell. It follows that, unless X-chromosome inactivation is perturbed in tumors a. all tumor cells in one mouse should express the same fluorescent protein (either red or green), but tumor cells from different mice can show either red or green fluorescence. b. the cells in any tumor should all express the same fluorescent protein (either red or green), but independently derived tumors in the same mouse can show either green or red fluorescence. c. different cells within each tumor can express different fluorescent proteins, and the tumors would therefore show yellow fluorescence, but each cell shows either red or green fluorescence. d. each cell can express both fluorescent proteins and would therefore emit yellow fluorescence, and the tumors would glow in yellow as well. e. different tumors would show red, yellow, or green fluorescence.
b
All of the following can be found in chromatin except a. DNA b. histones c. RNA d. transcription factors
c
Chromatin in which f the following states is the most euchromatic? a. in a Barr body b, in the centromere c. in a transcribed gene during G1 d. In a silenced gene during M phase e. in a sperm nucleus
c
DNA repair enzymes preferentially repair mismatched bases on the newly synthesized strand using the old DNA strand as a template. If mismatches were repaired instead without regard for which strand served as the template, a. indiscriminate mismatch repair would result in fewer mutations b. indiscriminate mismatch repair would result in more mutations c. there would be the same number of mutations as there would have been without any repair at all
c
During DNA replication, the single-strand DNA-binding (SSB) proteins a. are generally found more on the leading strand than the lagging strand. b. bind cooperatively to single-stranded DNA and cover the bases to prevent base-pairing. c. prevent the folding of the single-stranded DNA. d. bind cooperatively to short hairpin helices that readily form in the single-stranded DNA. e. All of the above.
c
During DNA replication, the single-strand DNA-binding (SSB) proteins ... A) are generally found more on the leading strand than the lagging strand. B) bind cooperatively to single-stranded DNA and cover the bases to prevent base-pairing. C) prevent the folding of the single-stranded DNA. D) bind cooperatively to short hairpin helices that readily form in the single-stranded DNA. E) All of the above.
c
How does a eukaryotic cell deal with the superhelical tension in its genomic DNA resulting from the activity of RNA polymerases? a. DNA gyrase introduces negative supercoils, keeping the DNA under constant tension b. The RNA polymerases are allowed to rotate freely around their templates during transcription, leading to the relaxation of the tension. c. DNA topoisomerases rapidly remove the superhelical tension caused by transcription. d. The nucleosomes adjust the tension by binding to positively supercoiled regions behind a moving RNA polymerase. e. All of the above.
c
Imagine a chromosome translocation event that brings a gene encoding a histone acetyl transferase enzyme from its original chromosomal location to a new one near heterochromatin. Which of the following scenarios is definitely NOT going to happen? A) The gene gets silenced due to heterochromatin expansion, leading to the misregulation of gene expression for a number of critical genes. B) The translocation event also brings along a chromatin barrier that can prevent heterochromatin expansion into the gene, and there is no phenotypic anomaly. C) Since the gene encodes a histone acetyl transferase, it resists heterochromatin expansion by acetylating its own histones. D) The level of the gene product decreases due to a position effect, leading to an imbalance in the chromatin state of the cell that results in the activation of programmed cell death.
c
Imagine a chromosome translocation event that brings a gene encoding a histone acetyl transferase enzyme from its original chromosomal location to a new one near heterochromatin. Which of the following scenarios is definitely NOT going to happen? a. the gene gets silenced during to heterochromatin expansion, leading to the misregulation of gene expression for a number of critical genes b. the translocation event also brings along a chromatin barrier that can prevent heterochromatin expansion into the gene, and there is no phenotypic anomaly c. since the gene encodes a histone acetyl transferase, it resists heterochromatin expansion by acetylating its own histones d. the level of the gene product decreases due to a position effect, leading to an imbalance in the chromatin state of the cell that results in the activation of programmed cell death
c
7. A DNA sequencing reaction contains which of the following? A) dideoxyribonucleoside triphosphates B) deoxyribonucleoside triphosphates C) DNA polymerase D) all of the above
d
Chloramphenicol blocks the peptidyl transferase reaction on ribosomes. Which of the following processes are inhibited? A) splicing B) 5' end capping C) base excision repair D) protein elongation
d
Comparing mRNA molecules from human Escherichia coli cells, which of the following is typically NOT true? A) A human mRNA has a special 5' cap, while a bacterial mRNA does not. B) A human mRNA has a poly-A tail, while a bacterial mRNA does not. C) A human mRNA undergoes alternative splicing, while a bacterial mRNA does not. D) A human mRNA contains noncoding sequences, while a bacterial mRNA does not. E) A typical human mRNA encodes one protein, while many bacterial mRNAs encode several different protein
d
DNA and RNA polymerase differ in all of the following EXCEPT a. the nucleotide substrates they incorporate b. their requirement for a primer c. their error rate. d. the type of chemical reaction they catalyze e. their processivity
d
DNA and RNA polymerase differ in all of the following EXCEPT... A) the nucleotide substrates they incorporate. B) their requirement for a primer. C) their error rate. D) the type of chemical reaction they catalyze. E) their processivity.
d
Due to their high transcription rate, active ribosomal RNA (rRNA) genes can be easily distinguished in electron micrographs of chromatin spreads. They have a characteristic "Christmas tree" appearance, where the DNA template is the "trunk" of the tree and the nascent RNA transcripts form closely packed "branches." At the base of each branch is an RNA polymerase extending that branch, while RNA processing complexes at the tip of the branch form terminal "ornaments." The top of the tree represents the ... of the rRNA gene, and the "ornaments" are at the ... end of the nascent rRNA molecules a. end; 3' b. end; 5' c. beginning; either 3' or 5' d. beginning; 3' e. beginning; 5'
d
For a nerve cell at its resting potential (-70 mV), the forces acting on potassium ions (K+) are a. none: K+ ions do not move at the resting potential b. an electrical gradient, pulling K+ inward, and a chemical gradient, pushing K+ inward c. an electrical gradient, pushing K+ outward, and a chemical gradient, pulling K+ inward d. an electrical gradient, pulling K+ inward, and a chemical gradient, pushing K+ outward e. an electrical gradient, pushing K+ outward, and a chemical gradient, pushing K+ outward
d
If the genome of the bacterium E. coli requires about 20 minutes to replicate itself, how can the genome of the fruit fly Drosophila be replicated in only 3 minutes? a. The Drosophila genome is smaller than the E. coli genome. b. Eukaryotic DNA polymerase synthesizes DNA at a much faster rate than prokaryotic DNA polymerase. c. The nuclear membrane keeps the Drosophila DNA concentrated in one place in the cell, which increases the rate of polymerization. d. Drosophila DNA contains more origins of replication than E. coli DNA.
d
