Genetics achieve questions for exam 2
To which part of the mRNA sequence does the RISC bind?
3' UTR
How does a bacterium protect its DNA from its own restriction enzymes?
Bacteria add methyl groups to their DNA so that restriction enzymes cannot recognize the cut site.
Cancer is fundamentally a genetic disease. Which statement does NOT correctly describe the genetic nature of cancer?
Cancer is only caused by mutations we inherit from our parents.
Consider the image. Which represents the 300 nm fibers?
D
What are CpG islands?
DNA regions with many cytosine bases adjacent to guanine bases DNA regions that form complexes with acetylase proteins
What are insulators?
DNA sequences that block the effect of enhancers in a position‑dependent manner
Determining the particular order of bases in a DNA molecule is known as _____.
DNA sequencing
How are siRNAs and miRNAs made?
Dicer processes and cleaves double‑stranded RNA to produce 21‑ to 25‑nucleotide‑long sequences.
True or false: The C value, which indicates the amount of DNA in a haploid genome, always correlates to the complexity of the organism.
False
The retinoblastoma (RB) protein acts to regulate cell cycle progression by mainly affecting which of these stages?
G1 to S
What is a major challenge faced by a molecular geneticist?
Genes only make up a small percentage of the total DNA in a cell.
Which of these puts the genetic changes associated with colon cancer in the CORRECT order? I: Activation of oncogene ras II: Loss of tumor-suppressor gene p53 III: Loss of antimetastasis gene IV: Loss of normal tumor-suppressor gene APC
IV, I, II, III
Initial knockout mice are chimeras containing cells with the disabled gene and cells with the wild-type gene. In order to study the phenotype of mice lacking the gene of interest, what is usually the next step?
Intercross the chimeric mice, and some of the progeny will be homozygous for the defective gene. (The chimeric mice contain some cells that have the gene knocked out; thus breeding them can produce mice that have the gene knocked out in all cells.)
Chronic myelogenous leukemia often results from a reciprocal translocation between chromosomes 9 and 22. How does this event lead to cancer?
It produces a fusion gene consisting of parts of the c-ABL and BCR genes, and this fusion gene acquires oncogenic activity.
What is the distinction between a benign tumor and a malignant tumor?
Malignant tumors invade other tissues.
_____ are mutations that arise randomly in the process of tumor development and do not contribute to cancer progression.
Passengers
_____ is initiated by double-stranded RNA molecules that are cleaved and processed.
RNA interference
Restriction enzyme I recognizes a 4 bp restriction site. Restriction enzyme II recognizes a 6 bp restriction site. On average, how does the number of restriction sites recognized by enzyme I compare to the number recognized by enzyme II?
Restriction enzyme I will have more restriction sites than enzyme II.
Why are retroviruses, in particular, associated with cancer?
Retroviruses insert their genome into the host genome, which could cause disruptions or expression changes in important genes.
What role does telomerase play in cancer formation and progression?
Telomerase prevents cell death triggered by shortened telomeres and is constitutively active in many cancers.
Why are transcriptional regulator proteins necessary?
The basal transcription apparatus can only produce minimal levels of transcription without them.
Why is it important that a cloning vector have a unique site for each restriction enzyme?
The presence of several restriction sites will generate multiple DNA fragments that cannot be easily reassembled.
How do response elements work to regulate transcription?
They are binding sites for transcriptional activators in response to stimuli.
Why are tumor-suppressor genes more difficult to identify than oncogenes?
To contribute to cancer, both copies of the tumor-suppressor gene must be mutated.
TRUE or FALSE. mtDNA and cpDNA contain rRNA and tRNA genes of their own for their organelle‑specific functions.
True
What is the definition of clonal evolution?
Tumor cells accumulate somatic mutations that allow them to become increasingly more aggressive in their proliferative properties.
What is the basal transcription apparatus?
a complex of RNA polymerase, transcription factors, and other transcription proteins
What is chromatin immunoprecipitation?
a technique that determines the specific locations within the genome where proteins interact with DNA
Assume that a tumor-suppressor gene is inactivated by an epigenetic event. What might you expect to find when sequencing this gene?
a wild-type DNA sequence that will show no changes
An RNA molecule has the percentages of bases shown: A = 30%, U = 23%, C = 20%, and G = 27%. What is the percentage of A in the template strand of DNA that encodes this RNA, assuming that the template strand contains no introns? a. 23% b. 30% c. 27% d. 20%
a. 23% (The percentage of A in the template would be 23% because A is complementary to U.)
_____ are found in prokaryotes, where they function in defense against foreign DNA. a. CRISPR RNAs b. Circular RNAs c. eRNAs d. Piwi-interacting RNAs
a. CRISPR RNAs
Which process affects gene regulation through alterations in chromatin structure? a. DNA methylation b. irreversible binding of a regulator protein c. point mutations d. mitosis
a. DNA methylation
Which statement is a feature of both prokaryotic and eukaryotic genes? a. DNA‑binding proteins influence the ability of RNA polymerase to initiate transcription of a gene. b. DNA must be unwound from histone proteins before transcription of a gene takes place. c. Genes are organized into operons. d. One promoter controls a cluster of genes. e. The nuclear membrane separates gene transcription and translation.
a. DNA‑binding proteins influence the ability of RNA polymerase to initiate transcription of a gene.
Which of these statements concerning ribozymes is correct? a. Degradation and cleavage of mRNA is dependent on the binding of regulatory molecules to a ribozyme sequence. b. Self-cleaving by ribozymes results in the translation of mRNA. c. Ribozymes primarily function through possession of anabolic activity toward RNA molecules. d. Ribozymes act independently in the cleaving of mRNA.
a. Degradation and cleavage of mRNA is dependent on the binding of regulatory molecules to a ribozyme sequence.
What occurs during the acquisition stage of the CRISPR-Cas system? a. Fragments of phage DNA are inserted into the bacterial CRISPR array. b. Foreign DNA from the same bacteriophage or plasmid enters the cell again. c. The CRISPR array is transcribed into a long CRISPR precursor RNA. d. Double-stranded RNA from viruses or long hairpins is cleaved by Dicer.
a. Fragments of phage DNA are inserted into the bacterial CRISPR array.
Which description about prokaryotic versus eukaryotic DNA replication is not correct? a. In prokaryotes, the DNA replication is unidirectional; in eukaryotes, the replication is bidirectional. b. In both prokaryotes and eukaryotes, the new and old DNA strands are assembled in antiparallel manner. c. In prokaryotes, there is only a single replication bubble; in eukaryotes, there are many. d. In both prokaryotes and eukaryotes, the DNA undergoes negative supercoiling during replication. e. In prokaryotes, there is only one origin of replication; in eukaryotes, there are many.
a. In prokaryotes, the DNA replication is unidirectional; in eukaryotes, the replication is bidirectional.
What is the function of the lac operator? a. It is bound by the lac repressor protein. b. It produces the lac repressor protein. c. It binds RNA polymerase. d. It binds lactose. e. It produces an initiator RNA molecule.
a. It is bound by the lac repressor protein.
Which statement describes the semiconservative model of DNA replication correctly? a. It proposes that the two nucleotide strands unwind and each serves as a template for a new DNA molecule. b. It proposes that the entire double‑stranded DNA molecule serves as a template for a whole new molecule of DNA. c. It proposes that both nucleotide strands break down into fragments, which then serve as templates for the synthesis of new DNA molecules.
a. It proposes that the two nucleotide strands unwind and each serves as a template for a new DNA molecule.
If a cell is simultaneously starved for most amino acids, including tryptophan, this general starvation affects the trp operon in a unique way. Because the ribosome stalls early in the translation of the leader peptide, region 1 in the mRNA 5′ UTR is able to pair with region 2. What effect will this have on the activity of the trp operon? a. It will result in reduced expression of the structural genes compared to when the cell is starved only for tryptophan. b. It will result in enhanced expression of the structural genes. c. The trp operon will be regulated normally. d. It will result in enhanced expression of the trpR repressor.
a. It will result in reduced expression of the structural genes compared to when the cell is starved only for tryptophan.
Which statement about cellular DNA in incorrect? a. Most cellular DNA is positively supercoiled. b. Supercoiling makes the separation of the two strands of DNA easier for replication and transcription. c. Supercoiling of cellular DNA is controlled by topoisomerases. d. Supercoiling allows cellular DNA to be packed into a small space. e. DNA exists in the cell as very long, tightly packed molecules.
a. Most cellular DNA is positively supercoiled.
Which of these statements about P bodies is INCORRECT? a. P bodies can't store mRNA molecules. b. Small interference RNA mediated RNA degradation also takes place in P bodies. c. P bodies can temporarily store mRNA molecules that may later be released. d. Most of the RNA degradation takes place in P bodies.
a. P bodies can't store mRNA molecules.
_____ RNA is an RNA molecule that aids in the processing of pre-mRNA. a. Small nuclear b. Messenger c. Transfer d. Ribosomal
a. Small nuclear (helps process pre-mRNA into mRNA)
Which of these statements is true about gene structure? a. The DNA can be much longer than that of mRNA originated from the gene. b. There is a direct correspondence between the nucleotide sequence of DNA and the amino acid sequence of a protein. c. Every codon in the eukaryotic gene encodes an amino acid. d. The number of nucleotides in a gene is always proportional to the number of amino acids in the protein encoded by that gene.
a. The DNA can be much longer than that of mRNA originated from the gene.
Which of the statements about the genetic code are most accurate? a. The genetic code is generally‑non‑overlapping. b. Three initiation codons set the three possible reading frames. c. An initiation codon sets the reading frame. d. The genetic code is generally overlapping. e. The promoter sets the reading frame.
a. The genetic code is generally‑non‑overlapping. c. An initiation codon sets the reading frame.
How do the rates of vertebrate mitochondrial DNA evolution compare to rates of vertebrate nuclear DNA evolution? a. Vertebrate mitochondrial DNA evolution is faster than vertebrate nuclear DNA evolution. b. There is not consistent pattern in rates of vertebrate mitochondrial DNA evolution. c. Vertebrate mitochondrial DNA evolution is slower than vertebrate nuclear DNA evolution. d. Vertebrate mitochondrial DNA evolution is equal to vertebrate nuclear DNA evolution.
a. Vertebrate mitochondrial DNA evolution is faster than vertebrate nuclear DNA evolution. (The accelerated rate of evolution seen in vertebrate mtDNA is due to its high mutation rate, which allows sequences to change more quickly.)
What is the role of the Sxl (sex-lethal) protein in the development of Drosophila? a. When it is inactive, male-specific splicing of dsx pre-mRNA occurs. b. When it is inactive, Tra and Tra-2 proteins direct female-specific splicing of the dsx pre-mRNA. c. When it is inactive, the Drosophila embryo will develop into a female. d. When it is active, it causes the tra pre-mRNA to be spliced to produce a nonfunctional protein.
a. When it is inactive, male-specific splicing of dsx pre-mRNA occurs.
What is a codon? a. a set of three mRNA nucleotides that codes for a specific amino acid b. an mRNA nucleotide occurring every three nucleotides that wobbles c. a set of three DNA nucleotides that codes for a specific amino acid d. a set of four mRNA nucleotides that codes for a specific amino acid e. a set of three DNA nucleotides that codes for specific mRNA nucleotides
a. a set of three mRNA nucleotides that codes for a specific amino acid
Eukaryotic DNA consists of a. all of these. b. highly repetitive DNA sequences. c. moderately repetitive DNA sequences. d. unique sequences of DNA.
a. all of these.
A group of antibiotics called 4-quinolones kill bacteria by a. binding to DNA gyrase. b. synthesizing a short stretch of RNA nucleotides. c. catalyzing DNA polymerization. d. adding new nucleotides to the 3' end of a growing DNA strand.
a. binding to DNA gyrase.
Which mechanism produces multiple mRNAs of different lengths encoding different polypeptides from a single gene? a. both alternative splicing and RNA editing b. trans-splicing c. alternative splicing d. RNA editing
a. both alternative splicing and RNA editing
What are the proteins that alter chromatin structure without altering the chemical structure of the histones directly? a. chromatin-remodeling complexes b. histone tails c. DNase I d. transcription factors
a. chromatin-remodeling complexes
When a solution containing double‑stranded DNA is heated, the hydrogen bonds that hold the two strands can be weakened and eventually broken, separating the strands completely. This process is called a. denaturation. b. hybridization. c. double‑strand break. d. renaturation.
a. denaturation.
Which mechanism allows rare bases to be incorporated into tRNA molecules? a. enzyme-mediated chemical modifications of normal RNA bases b. spontaneous chemical modifications of normal RNA bases c. RNA editing d. RNA trimming
a. enzyme-mediated chemical modifications of normal RNA bases
Which genes would likely be part of the same operon? Gene A = defense against other bacteria Gene B = defense against bacteriophages Gene C = carbohydrate metabolism Gene D = cell motility protein Gene E = toxin production a. genes B, E, A b. genes A, B, D c. genes D, C, A d. genes D, C, E
a. genes B, E, A
Where are Group I introns found? a. genes of bacteria, bacteriophages, and eukaryotes b. genes of bacteria, archaea, and eukaryotic organelles c. protein-encoding genes in the nucleus of eukaryotes d. tRNA genes of bacteria, archaea, and eukaryotes
a. genes of bacteria, bacteriophages, and eukaryotes
Most of the centromere and telomere structures consist of a. heterochromatin b. euchromatin c. kinetochore d. GC repeats
a. heterochromatin
A mutation that destroys the function of a promoter would affect which stage of transcription? a. initiation b. elongation c. termination d. replication
a. initiation
Which of these is NOT involved in the unwinding process of replication in E. coli? a. initiator proteins b. helicase c. gyrase d. single-strand-binding proteins
a. initiator proteins
Which organelle or organelles contain DNA of their own? Select all that apply. a. mitochondria b. endoplasmic reticulum c. Golgi apparatus c. chloroplasts
a. mitochondria c. chloroplasts
When a circular DNA gets underrotated by the action of cellular enzymes, the DNA is said to exhibit a. negative supercoiling. b. bubbling. c. positive supercoiling. d. relaxed state.
a. negative supercoiling.
Which of the options are mechanisms of mRNA surveillance? a. no‑go decay b. tRNA mediated mRNA decay c. nonsense‑mediated mRNA decay d. premature‑termination mediation e. nonstop mRNA decay
a. no‑go decay c. nonsense‑mediated mRNA decay e. nonstop mRNA decay
As DNA unwinds during replication, the antiparallel nature of the two DNA strands means that a. one template is exposed in the 5' to 3' direction and the other template is exposed in the 3' to 5' direction. b. both templates are exposed to the 5' to 3' direction. c. both templates are exposed to the 3' to 5' direction. d. new DNA strands always elongate in the same 3' to 5' direction.
a. one template is exposed in the 5' to 3' direction and the other template is exposed in the 3' to 5' direction.
Which type of RNA molecule is derived from a long single-stranded RNA transcript and is known to suppress the expression and movement of transposons in the animal germ cells? a. piRNA b. snoRNA c. siRNA d. miRNA
a. piRNA
Which is not a variation of splicing? a. progressive splicing b. self‑splicing c. recursive splicing d. trans‑splicing e. minor splicing
a. progressive splicing
The point of unwinding, where the two strands separate from the double-stranded DNA helix, is called a a. replication fork. b. replicon. c. replication bubble. d. bidirectional replication.
a. replication fork.
In eukaryotes the initiation of replication can be separated into two steps. Which of the steps listed is the second? a. replication machinery initiates replication at a licensed origin b. origin recognition complex binds to an origin c. replication licensing factors attach to an origin d. a step that takes place early in the cell cycle
a. replication machinery initiates replication at a licensed origin
Selene is targeting RNA molecules for a function test. She introduces a molecule that signals a cascade that causes the lysosome to degrade the nucleus. Which of these molecules would not be immediately affected by the action of the lysosome? a. tRNA b. mRNA c. snRNA d. pre-mRNA
a. tRNA
Which of these is not involved in the initiation of translation in bacteria? a. tRNA carrying the next amino acid that will occupy the A site b. mRNA c. tRNA carrying N-formylmethionine that will occupy the P site d. small and large ribosomal subunits e. GTP and initiation factors
a. tRNA carrying the next amino acid that will occupy the A site
What is the Shine-Dalgarno sequence? a. the ribosome binding site in bacterial RNA b. the ribosome binding site in eukaryotic RNA c. three nucleotides that code for a specific amino acid d. the sequence of nucleotides at the 3' end of the RNA molecule that does not code for amino acids e. the sequence of nucleotides at the 5' end of the RNA molecule that codes for amino acids
a. the ribosome binding site in bacterial RNA
What is the function of elongation factor Ts in elongation? a. to regenerate EF-Tu-GTP from EF-Tu-GDP b. to facilitate the formation of peptide bonds between the amino acids in the ribosome c. to move the ribosome down the mRNA d. to complex with GTP and a charged tRNA and bind to the A site
a. to regenerate EF-Tu-GTP from EF-Tu-GDP (
A gene's promoter is usually found _____ of the transcription initiation site. a. upstream b. near the end c. downstream d. in the middle of
a. upstream (The transcription unit needs to bind to the promoter before proceeding downstream.)
An advantage of using an adenovirus as a gene vector in gene therapy is that:
adenoviruses transfer DNA to nondividing cells.
Which statements about primers are correct? a. They are synthesized by an enzyme called primase. b. They are synthesized by DNA polymerase α. c. They provide a 3′−OH3′−OH group for attachment of DNA nucleotides. d. They are needed for the start of DNA synthesis.
all of them
Proteins are composed of_____ linked togethery by_______ bonds.
amino acids; peptide
If the sequence of an RNA molecule is 5′-GGCAUCGACG-3′, what is the sequence of the nontemplate strand of DNA? a. 3′-GGCATCGACG-5′ b. 5′-GGCATCGACG-3′ c. 3′-CCGTAGCTGC-5′ d. 5′-CCGTAGCTGC-3′
b. 5′-GGCATCGACG-3′
The amount of DNA in one set of chromosomes in an organism is termed its a. genome. b. C-value. c. sequence. d. n value.
b. C-value (Eukaryotic organisms vary dramatically in the amount of DNA per cell, which is a quantity termed an organism's C-value.)
The chemical named camptothecin was purified from the happy tree, a rare plant native to China, and its derivatives have shown therapeutic effect against certain cancers. How do camptothecin compounds work as chemotherapeutic agent to kill cancer cells? a. Camptothecin is known to activate cellular nucleases inside the cell and cause DNA to be cleaved, which subsequently causes cell death. b. Camptothecin inhibits the removal of supercoiling ahead of replication, causing DNA damage and subsequent cell death. c. Camptothecin poisons DNA polymerase I and allows the RNA primers to stay on. d. Camptothecin prevents initiator protein from binding to initiate DNA replication.
b. Camptothecin inhibits the removal of supercoiling ahead of replication, causing DNA damage and subsequent cell death.
What property of the DNA molecule explains the necessity for Okazaki fragments? a. DNA is negatively charged. b. DNA is antiparallel. c. DNA is a linear molecule. d. DNA is wound around histones.
b. DNA is antiparallel.
Which component required for prokaryotic DNA replication is not involved in "unwinding" the DNA template? a. DNA gyrase b. DNA ligase c. initiator proteins d. DNA helicase e. single‑strand binding proteins
b. DNA ligase
_____ would always produce hybrid molecules containing some original and some new DNA, but the proportion of new DNA within the molecules would increase with each replication event. a. Linear eukaryotic replication b. Dispersive replication c. Conservative replication d. Semiconservative replication
b. Dispersive replication
Which statement is most consistent with the one gene, one enzyme hypothesis originally proposed by Beadle and Tatum? a. A gene can only make one enzyme in a cell cycle. b. Every gene encodes a separate enzyme. c. Each gene makes one enzyme but not one protein. d. Genes and enzymes are important. e. Every enzyme makes one gene.
b. Every gene encodes a separate enzyme.
Which statement is correct about the reassembly of nucleosomes during replication? a. This step is performed by the replication licensing factor. b. Histones from the original DNA duplex are mixed with new histones on the two new DNA molecules. c. Only new histones are incorporated into the two new DNA molecules following replication. d. Only histones from the original DNA duplex are incorporated into the two new DNA molecules.
b. Histones from the original DNA duplex are mixed with new histones on the two new DNA molecules.
Which statement describes the conservative model of DNA replication correctly? a. It proposes that the two nucleotide strands unwind and each serves as a template for a new DNA molecule. b. It proposes that the entire double‑stranded DNA molecule serves as a template for a whole new molecule of DNA. c. It proposes that both nucleotide strands break down into fragments, which then serve as templates for the synthesis of new DNA molecules.
b. It proposes that the entire double‑stranded DNA molecule serves as a template for a whole new molecule of DNA.
_____ carries genetic information from DNA to a ribosome where it helps assemble amino acids in their correct order. a. A codon b. Messenger RNA c. The protein-coding region d. The poly (A) tail
b. Messenger RNA
You are researching a new antibiotic and discover that it prevents translation by blocking the binding of Met-tRNAIMet. Do you think your antibiotic has promise in the medical field? a. No; the ribosome would utilize a different charged tRNA to begin initiation and continue translation. b. No; Met-tRNAIMet is the eukaryotic initiator tRNA, so you would be preventing translation in your patient's human cells. c. Yes; if you prevent the large ribosomal subunit from binding, initiation cannot happen. d. Yes; if you prevent Met-tRNAIMet from binding, then you prevent initiation and thus translation.
b. No; Met-tRNAIMet is the eukaryotic initiator tRNA, so you would be preventing translation in your patient's human cells.
Which evidence supports the assumption that, over evolutionary time, DNA sequences have moved from mitochondria and chloroplasts to the nucleus? a. Mitochondrial DNA is replicated by a different DNA polymerase. b. Nuclear genes that encode organelle proteins are most similar to eubacterial genes. c. Organelle DNA is circular. d. Nuclear genes are found only in eukaryotes, and similar genes are never found in bacteria.
b. Nuclear genes that encode organelle proteins are most similar to eubacterial genes. (The endosymbiotic theory proposes that mitochondria were at one time free-living eubacteria. If the genes were transferred from the organelles to the nucleus, you would expect that these genes would be more similar to eubacterial genes than eukaryotic genes.)
What are CRISPR RNAs? a. RNAs found in the germ cells of animals that inhibit transposons. b. RNAs found in prokaryotes that function in defense against foreign DNA. c. RNAs found in all cell types that assist in the processing of rRNA. d. RNAs found in eukaryotes that assist in the processing of pre‑mRNA. e. RNAs found in eukaryotes that can degrade mRNA to control gene expression.
b. RNAs found in prokaryotes that function in defense against foreign DNA.
Which of these sequences exhibit full consensus based on the nucleotide set shown? A G G A G T T C A G C T A T T C T G C A A T A C T C G A A A A G T C C T A A T G T G C A A T T C a. T C G A A T T G b. T G C A A T T C c. A C G T G A A C d. T G C A A A A G
b. T G C A A T T C
Which of these events is NOT required in order to induce termination of the transcription process? a. The newly made RNA molecule must be released from the polymerase. b. The RNA molecule partially dissociates from the DNA molecule. c. The RNA polymerase must detach from the DNA template. d. RNA polymerase halts synthesis RNA after the terminator sequence is transcribed.
b. The RNA molecule partially dissociates from the DNA molecule.
Which statement is not a characteristic of transcriptional activator proteins? a. They are capable of binding DNA at a consensus sequence of a regulatory promoter. b. They are capable of binding DNA at a consensus sequence in the protein‑coding part of the gene. c. They contain one or more DNA‑binding motifs. d. They can interact with other components of the transcriptional apparatus. e. They can influence the rate of transcription.
b. They are capable of binding DNA at a consensus sequence in the protein‑coding part of the gene.
Which statement is not correct about how siRNAs and miRNAs function? a. They are found in eukaryotes. b. They can integrate into DNA sequences of specific genes. c. They can repress translation from specific mRNA molecules. d. They can mediate the destruction of specific mRNA molecules. e. They interact with the RISC complex.
b. They can integrate into DNA sequences of specific genes.
If regions 2 and 3 of the 5' UTR trp operon base pair to form a hairpin, will the structural genes be transcribed? a. No, this hairpin is an attenuator, so transcription would be stopped. b. Yes, this hairpin does not prevent transcription. c. Yes, this hairpin is an attenuator. d. No, this hairpin is an antiterminator.
b. Yes, this hairpin does not prevent transcription.
An individual unit of replication is referred to as a. a negative supercoil. b. a replicon. c. a replication fork. d. a double helix. e. antiparallel.
b. a replicon.
Which choice is the true inducer of the lac operon? a. galactose b. allolactose c. glucose d. lactose e. cAMP
b. allolactose
The process by which mRNA can be spliced so that two distinct proteins, such as the large T antigen and small t antigen of T cells, can be produced is called a. diverse splicing. b. alternative splicing. c. conservative splicing. d. mixed splicing.
b. alternative splicing. (Alternative splicing allows pre-mRNA to be spliced in multiple ways, generating different proteins in different tissues or at different times in development.)
A small RNA that can base pair with an mRNA molecule and affects its functioning is called a. an activator. b. an antisense RNA. c. a repressor. d. an inducer. e. a riboswitch.
b. an antisense RNA.
What is the role of the acceptor arm of the tRNA molecule? a. binding to the codon sequence in the DNA b. binding a specific amino acid c. binding to the growing polypeptide chain d. binding to the codon sequence of the mRNA e. binding to the ribosome
b. binding a specific amino acid
In the trp operon, in the absence of tryptophan, the trp repressor a. binds to the regulator gene and represses transcription. b. cannot bind to the operator, so transcription takes place. c. binds to the operator and represses transcription. d. cannot bind to the regulator gene, so transcription takes place.
b. cannot bind to the operator, so transcription takes place. (Without tryptophan, the repressor will not bind and transcription will continue.)
A bacterial cell is grown in the presence of both glucose and lactose. Over time, a researcher measures the amount of glucose and lactose that have been used by the cells. She finds that glucose levels are reduced, but lactose levels have remained constant. She proposes that these bacterial cells are exhibiting a. catabolite activation. b. catabolite repression. c. positive control. d. metabolite attenuation.
b. catabolite repression.
DNA from a eukaryotic gene was isolated, denatured, and hybridized to the mRNA transcribed from the gene. The hybridized structure was then observed with an electron microscope. The image is shown. Based on these results, the gene must contain _____ exons and _____ introns. a. four; five b. five; four c. five; five d. four; four
b. five; four
If a gene were arranged like the figure, how many different mRNAs with at least two exons are possible through alternative splicing? a. three b. four c. two d. one
b. four
What secondary structure forms in the 5' UTR of the trp operon when tryptophan levels are high? a. hairpin between regions 1 and 2 b. hairpin between regions 3 and 4 c. hairpin between regions 1 and 4 d. hairpin between regions 2 and 3
b. hairpin between regions 3 and 4 (High levels of tryptophan covers region 2 and leads to a hairpin structure between 3 and 4.)
When tryptophan levels are _____, regions _____ of the 5' UTR pair, followed by a string of uracil nucleotides. a. low; 1 and 4 b. high; 3 and 4 c. high; 2 and 3 d. low; 3 and 4
b. high; 3 and 4
A mutation at the operator site prevents the regulator protein, which acts as a repressor, from binding. Constitutive expression results from the operon. This is an example of a (n) _____ operon. a. promotive b. inducible c. positive control d. repressible
b. inducible (In an inducible operon, transcription is off due to a repressor binding, and an inducer must be present to relieve the repression.)
Paul is genotyping RNA molecules in the lab. He finds the diagram shown. Which of these steps can be taken for translation to take place? a. modifying segment A through addition of nucleotides to the 5' end b. introduce a marker dissociating substance B from the molecule c. adding a stabilizer to be interjected before segment A d. modifying the ribosome-binding site
b. introduce a marker dissociating substance B from the molecule
Which modes of replication is bidirectional, antiparallel, both continuous and discontinuous, and has multiple replicons? a. rolling‑circle replication b. linear eukaryotic replication c. theta replication
b. linear eukaryotic replication
A student discovers a small amount of DNA in a test tube but doesn't know its origin. She finds that it has no associated histone proteins and is circular. This DNA is most likely from which genome? a. plant nuclear DNA b. mitochondrial DNA c. human sex chromosomes d. eukaryotic nuclear DNA
b. mitochondrial DNA (Mitochondrial DNA has no associated histones and is circular.)
How many promoters are typically found in a four-gene operon? a. four b. one c. two d. three
b. one (An operon only contains one promoter within the group of genes.)
Telomerase has a(n) _____ and a(n) _____ component. a. enzyme; base b. protein; RNA c. enzyme; sugar d. protein; DNA
b. protein; RNA
The enzymes that are known to degrade cellular RNA are called a. exonucleases. b. ribonucleases. c. DNase I. d. methyltransferases.
b. ribonucleases.
Based on the most recent evidence, what would be the most likely result of expressing telomerase in somatic cells in humans? a. longer life with fewer age-related changes due to stabilization of chromosomes b. shorter life due to promotion of cancer c. shorter life due to shortening and destabilization of chromosomes d. longer life due to resistance to cancer
b. shorter life due to promotion of cancer
What is the purpose of a telomere? a. guides the chromosome through meiosis b. stabilizes the end of a chromosome c. acts as a site of attachment for spindle fibers in a chromosome d. joins two or more chromosomes together
b. stabilizes the end of a chromosome (Telomeres serve as caps that stabilize the chromosome and also provide a means of replicating the ends of a chromosome.)
Which does the termination of translation require? a. E site of the ribosomal complex b. stop codon on the mRNA c. release factors d. terminator tRNA e. GTP
b. stop codon on the mRNA c. release factors e. GTP
In which type of RNA do rare modified bases occur including ribothymidine, pseudouridine, and dozens of others? a. mRNA b. tRNA c. pre-mRNA d. snRNA
b. tRNA
The structure of tRNA described as L-shaped is the _____ structure. a. quaternary b. tertiary c. secondary d. primary
b. tertiary
A scientist wishes to investigate if a region of DNA within a pancreas cell is being actively transcribed in response to insulin. What would she look for as evidence of active regions of DNA transcription? a. if the DNA is being replicated during insulin treatment b. the ability of DNase I to cleave specific sites within the DNA c. increased level of methylation within CpG islands d. the number of nucleosomes within the nucleus
b. the ability of DNase I to cleave specific sites within the DNA
Which is the most precise definition of a gene? a. all sequences of DNA that code for an RNA molecule b. the entire DNA sequence that is required to transcribe and encode a single RNA molecule c. the sequence of nucleotides that codes for amino acids in a protein d. all sequences of DNA that code for a single mRNA molecule e. all DNA sequences that code for a particular inherited trait
b. the entire DNA sequence that is required to transcribe and encode a single RNA molecule
Which component of translation is frequently targeted by antibiotics? a. the template mRNA b. the ribosome c. tRNAs d. aminoacyl‑tRNA synthetase e. IF‑2
b. the ribosome
What is the purpose of the antibody in a crosslinked ChIP (xChIP) assay? a. to fragment the chromatin into many DNA fragments b. to separate the DNA fragments bound to the protein of interest from the DNA fragments that are not bound c. to crosslink the DNA and proteins together d. to determine the sequence of the DNA
b. to separate the DNA fragments bound to the protein of interest from the DNA fragments that are not bound
Chromosomal puffs on polytene chromosomes in Drosophila indicate areas of active a. translation b. transcription c. replication d. metabolism.
b. transcription (The correlation between the occurrence of transcription and the relaxation of chromatin at a puff site indicates that chromatin structure undergoes dynamic change associated with gene activity.)
Since eukaryotic gene expression is separated by space and time, _____ occurs first in the nucleus and _____ happens after in the cytoplasm. a. stimulation; repression b. transcription; translation c. translation; transcription d. initiation; termination
b. transcription; translation
What would be the minimum codon size (number of nucleotides) required if the number of different types of amino acids in proteins were 12? a. one b. two c. four d. three
b. two (If codons consisted of two nucleotides, then 16 codons would be possible, which is more than enough to encode 12 amino acids.)
Which of the mechanisms is not a mechanism of action of RNA inference? a. transcriptional silencing b. ubiquitination of proteins c. degradation of mRNA d. cleavage of mRNA e. inhibition of translation
b. ubiquitination of proteins
An enhancer is typically found _____ from the promoter, but its effect is _____ its location on the gene. a. downstream; independent of b. upstream; dependent on c. upstream; independent of d. downstream; dependent on
b. upstream; dependent on c. upstream; independent of
If a theoretical organism has a total of 25 different amino acids found in its proteins, how many different tRNAs would this organism need to possess? a. 28 b. 50 c. 25 d. 20
c. 25
Which activity of DNA polymerases in E. coli allows them to remove a nucleotide that has been inserted incorrectly? a. 3' to 5' endonuclease b. 5' to 3' polymerase c. 3' to 5' exonuclease d. 5' to 3' exonuclease
c. 3' to 5' exonuclease
Which of these statements is TRUE concerning the difference between DNA replication and transcription? a. The majority of DNA encodes functional products for use in transcription. b. DNA replication is a more selective process than transcription. c. A fundamental difference is the length of nucleotides required for the process. d. All gene products are needed at the same time in transcription.
c. A fundamental difference is the length of nucleotides required for the process.
In the beginning of the gene depicted, what region is represented by A, and what region is represented by B? a. A represents the regulatory promoter; B represents the core promoter and the activator binding site. b. A represents the core promoter; B represents the regulatory promoter and the activator binding site. c. A represents the regulatory promoter and the activator binding site; B represents the core promoter. d. A represents the core promoter and the activator binding site; B represents the regulatory promoter.
c. A represents the regulatory promoter and the activator binding site; B represents the core promoter.
Which statement about the genetic code is NOT true? a. A coding region is read 5' to 3' on mRNA. b. A coding region is punctuated with start and stop signals. c. A single codon can normally specify more than one amino acid. d. A coding region is read in groups of three adjacent nucleotides on mRNA.
c. A single codon can normally specify more than one amino acid. (Normally, a single codon can specify no more than one amino acid. Note that the three stop codons do not specify any amino acid at all.)
All of these repeated sequences can be found in telomeres EXCEPT a. TTAGGC. b. TTGGGG. c. CCGGGG. d. TTAGGG.
c. CCGGGG. (Telomeres take the form 5'−(A or T)mGn−3', where m ranges from one to four and n is two or more.)
In the experiment showing the noncolinearity of eukaryotic genes, which molecule is the longest? a. RNA b. mRNA c. DNA d. tRNA
c. DNA
If the promoter that best matches the consensus sequence shown serves as the strongest promoter, then which sequence would serve as the strongest promoter? G C Y A T R N A a. G C G A T T C G b. G C A A T A G A c. G C C A T A A A d. G G T A T C T A
c. G C C A T A A A
The eukaryotic protein critical for organizing chromatin structure is histone. Which histone protein is not included in the histone "core" that is often described as the "beads"? a. H2B b. H4 c. H1 d. H2A e. H3
c. H1
Shown are the steps that comprise the initiation of RNA synthesis. What is the correct sequence of these steps? I. creation of the first bonds between rNTPs II. formation of a transcription bubble III. escape of the transcription apparatus from the promoter IV. promoter recognition a. II, IV, III, I b. IV, I, II, III c. IV, II, I, III d. I, II, III, IV
c. IV, II, I, III
Which feature of RNA makes it less stable and more likely to be degraded compared to DNA? a. It contains U instead of T. b. It can fold back on itself to form double-stranded stems and single-stranded loops. c. It has a free hydroxyl group on the 2' carbon of ribose. d. It usually consists of only a single strand of nucleotides.
c. It has a free hydroxyl group on the 2' carbon of ribose.
Which reaction normally happens in the regulation of the trp operon when high levels of tryptophan are present? a. Regions 2 and 4 will pair in the attenuation region in the 5′' UTR of the RNA. b. Regions 2 and 3 will pair in the attenuation region in the 5' UTR of the RNA. c. Regions 3 and 4 will pair in the attenuation region in the 5′ UTR of the RNA. d. The trp activator protein will be produced. e. The trp repressor will become inactivated.
c. Regions 3 and 4 will pair in the attenuation region in the 5′ UTR of the RNA.
What would happen if eukaryotic cells did not go through licensing in the process of replication? a. Replication would be initiated at thousands of origins only once. b. One origin of replication would be initiated. c. Some genes would not be replicated while others would be replicated more than once. d. Each gene would only be replicated once.
c. Some genes would not be replicated while others would be replicated more than once.
Which is not a characteristic of the 5' cap? a. The 5' cap influences the removal of introns. b. The 5' cap is added to the mRNA by a 5'-5' phosphodiester bond. c. The 5' cap is a tag for mRNA degradation. d. The 5' cap increases the stability of the mRNA molecule. e. The 5' cap facilitates the binding of the ribosome to the mRNA.
c. The 5' cap is a tag for mRNA degradation.
Which statement about chromatin organization is NOT true? a. Heterochromatin is more highly condensed than euchromatin. b. Actively transcribed genes are found primarily in euchromatin. c. The default (normal) condition of all chromatin is to be transcriptionally active. d. Chromatin consists primarily of DNA and histone proteins.
c. The default (normal) condition of all chromatin is to be transcriptionally active. (At any one time, only a small fraction of the genome is transcribed, and most genes are sequestered from the transcription machinery within tight coils and loops of chromatin.)
Which statements about euchromatin and heterochromatin are correct? Select all that apply. a. Most genes are present in heterochromatin. b. Euchromatin largely consists of repeated sequences. c. The majority of transcription takes place on euchromatin. d. Heterochromatin is less condensed than euchromatin. e. Euchromatin undergoes condensation and decondensation throughout the cell cycle.
c. The majority of transcription takes place on euchromatin. e. Euchromatin undergoes condensation and decondensation throughout the cell cycle.
You have isolated a protein that you hypothesize to be a transcriptional activator. What is one characteristic of the protein that would support your hypothesis? a. When the protein is absent from a cell, the rate of transcription does not change. b. The protein has the ability to reposition nucleosomes. c. The protein contains helix-turn-helix and zinc-finger motifs. d. The protein can bind RNA.
c. The protein contains helix-turn-helix and zinc-finger motifs.
Which of these statements about transcriptional repressors is correct? a. These repressors bind to the core promoter region. b. Similar to the bacterial repressor, the eukaryotic repressor can block RNA polymerase. c. The repressors may compete with activators for the same DNA binding site. d. The main role of repressors is to inhibit the translation of the gene that has been transcribed.
c. The repressors may compete with activators for the same DNA binding site.
In your bacterial translation experiment, you notice that you keep producing proteins with incorrect amino acids, based on the sequence of the mRNA. What is one possible reason you are seeing this? a. There are not enough tRNA molecules in your reaction. b. The mRNA is mutating before it is translated by the ribosome. c. The ribosome you are using is defective in its proofreading function. d. The original DNA sequence has mutations in it.
c. The ribosome you are using is defective in its proofreading function. (After translocation, the ribosome checks the interaction between the mRNA and the tRNA in the P site. If the wrong tRNA was added, the alignment between the mRNA and tRNA will be incorrect, triggering premature termination of translation.)
What would likely happen if poly (A)-binding proteins were irreversibly bound to the poly (A) tail of the mRNA? a. The mRNA would be degraded immediately. b. The poly (A)-binding proteins would begin to remove nucleotides from the 5' end. c. This would increase the stability of the mRNA. d. The removal of the 5' cap would speed up.
c. This would increase the stability of the mRNA.
In an inducible operon, an inducer molecule will bind to a regulatory protein to facilitate its action upon the operon, often by altering the shape of the protein. These types of regulatory proteins are called _____ proteins. a. initiator b. inducible c. allosteric d. constitutive
c. allosteric (Allosteric proteins create conformational changes when bound to another molecule.)
Proteins that change shape on binding to another molecule are called a. activator proteins. b. structural proteins. c. allosteric proteins. d. antisense proteins. e. inducible proteins.
c. allosteric proteins.
If tetracycline binds to the A site of the bacterial ribosome, how does that prevent translation? a. induces translational errors b. blocks peptide bond formation c. blocks charged tRNAs from binding to the ribosome d. blocks translocation
c. blocks charged tRNAs from binding to the ribosome (Tetracyclines are a class of antibiotics that bind to the A site of a bacterial ribosome and block the entry of charged tRNAs, yet they have no effect on eukaryotic ribosomes.)
What poisons the topoisomerase so that it is unable to remove supercoils ahead of replication? a. DNA polymerases b. topoisomerase enzymes c. camptothecin compounds d. gyrase
c. camptothecin compounds
The DNA sequences that are capable of affecting transcription at distant promoters, sometimes tens of thousands of base pairs away, are referred to as a. coactivators. b. mediators. c. enhancers. d. insulators.
c. enhancers.
In what kind of cell would you find an mRNA closed loop structure? a. neither bacterial nor eukaryotic b. bacterial c. eukaryotic d. both bacterial and eukaryotic
c. eukaryotic (The 3' end of mRNA bends over and associates with the 5' cap during the initiation of translation, forming a circular structure known as a closed loop)
The function of sigma factor in bacteria is replaced by that of _____ in eukaryotes. a. RNA polymerase b. transcriptional activator proteins c. general transcription factors d. enhancers
c. general transcription factors (General transcription factors along with RNA polymerase form the basal transcription apparatus that binds to promoters in eukaryotes to initiate transcription.)
Telomeres and centromeres are found in a. LINEs and SINEs. b. moderately repetitive DNA. c. highly repetitive DNA. d. unique-sequence DNA.
c. highly repetitive DNA. (Highly repetitive sequences are clustered in certain regions of the chromosome, especially in centromeres and telomeres.)
Inhibition of gene expression triggered by double-stranded RNA molecules is termed RNA a. removal. b. inhibition. c. interference. d. mutation.
c. interference.
In eukaryotes, noncoding sequences that interrupt the coding regions are called a. UTRs. b. codons. c. introns. d. exons.
c. introns.
What is the Β(beta) sliding clamp? a. it synthesizes short stretches of RNA nucleotides b. an initiator of E. coli DNA replication c. it encircles the DNA and allows the polymerase to slide easily d. a single origin of replication
c. it encircles the DNA and allows the polymerase to slide easily
If you wanted to ensure replication with fewer mistakes, would you use a polymerase that had a more open or more closed active site? Why? a. more closed, because replication happens slower with these polymerases thus fewer mistakes are made b. more open, because your gene may have bulky lesions and only a polymerase with a more open site would be effective c. more closed, because this polymerase makes fewer mistakes than one with an open active site d. more open, because then the gene could be replicated at great speed
c. more closed, because this polymerase makes fewer mistakes than one with an open active site
Which statement best describes chromatin associated with actively transcribed genes as compared to chromatin associated with genes which are not being actively transcribed? a. more relaxed and less acetylated b. more compacted and less acetylated c. more relaxed and more acetylated d. more compacted and more acetylated
c. more relaxed and more acetylated (Acetylation of histone tails causes the histones to loosen their grip on DNA so that the genetic information is more accessible to the transcriptional machinery.)
When tryptophan levels are high, transcription terminates at the end of the trp operon because the ribosome can a. stall at the two UGG codons in region 2 of the 5' UTR. b. stall at the two UGG codons in region 1 of the 5' UTR. c. move quickly through the two UGG codons in region 1 of the 5' UTR. d. move quickly through the two UGG codons in region 2 of the 5' UTR.
c. move quickly through the two UGG codons in region 1 of the 5' UTR.
A _____ enzyme consists of several individual polypeptide chains. a. ribozyme b. sigma c. multimeric d. promoter
c. multimeric
The trp operon is an example of a _____ and _____ operon. a. positive; inducible b. positive; repressible c. negative; repressible d. negative; inducible
c. negative; repressible
Which processes ensure the high accuracy of replication? a. linear replication b. replication licensing c. nucleotide selection d. mismatch repair e. proofreading
c. nucleotide selection d. mismatch repair e. proofreading
A mutant strain of E. coli produces β-galactosidase in the presence and in the absence of lactose. The mutation in this operon lies in the a. lac promoter. b. lacZ gene. c. operator. d. the structural gene for the CAP protein.
c. operator.
Which choice is not a mechanism of gene regulation that can take place after transcription is completed in eukaryotes? a. RNA interference b. mRNA degradation c. polymerase stalling d. RNA cleavage by siRNA e. RNA splicing
c. polymerase stalling
The type of transcriptional control in operons in which a regulatory protein is an activator and stimulates transcription is called a. attenuation. b. induction. c. positive control. d. repression. e. negative control.
c. positive control.
A particular mutation occurs resulting in the changing of the branch point A within an intron to a U. What is the most likely effect of this mutation? a. production of a normal mRNA but an abnormal protein product b. production of a normal mRNA and protein product c. production of a longer-than-normal mRNA and an abnormal protein product d. production of a shorter-than-normal mRNA and an abnormal protein product
c. production of a longer-than-normal mRNA and an abnormal protein product
Most amino acids are similar in structure. Which component can, and does, differ between them? a. amino group b. hydrogen atom c. radical group d. carboxyl group
c. radical group (The different R groups help determine the chemical properties of the amino acids.)
The bacterial transfer‑messenger RNA system a. restores normal translation of the gene by a stalled ribosome. b. mediates the interaction of tRNAs with mRNA. c. removes stalled ribosomes in bacteria. d. directly targets the mRNA with a stalled ribosome for degradation. e. generates truncated proteins.
c. removes stalled ribosomes in bacteria.
Which mode of replication is unidirectional, antiparallel, continuous, and is initiated by a single break on the outer strand? a. linear eukaryotic replication b. theta replication c. rolling‑circle replication
c. rolling‑circle replication
What is the first stage of protein synthesis? a. the assembly of transcription factors at the promoter b. initiation, in which the components necessary for translation are assembled at the ribosome c. tRNA charging, in which the tRNAs bind to amino acids d. setting the reading frame, where the initiation codon is recognized by RNA polymerase e. elongation, in which amino acids are joined to the polypeptide chain
c. tRNA charging, in which the tRNAs bind to amino acids
Which mRNA sequence does not play a role in intron splicing? a. an adenine nucleotide 18-40 nucleotides upstream of the 3' splice site b. the branch point c. the Shine-Dalgarno sequence d. the 3' splice site e. the 5' splice site
c. the Shine-Dalgarno sequence
In a polyribosome, the polypeptides associated with which ribosomes will be the longest? a. those in the middle of mRNA b. All polypeptides will be the same length. c. those at the 3' end of mRNA d. those at the 5' end of mRNA
c. those at the 3' end of mRNA (Ribosomes at the 3' end of mRNA are reaching completion of translation and will contain longer polypeptides.)
The compound camptothecin and its derivatives are used as effective chemotherapeutic drugs for treating cancer. Which enzyme is the target of camptothecin for disruption of DNA replication in cancer cells? a. DNA polymerase δ b. DNA ligase c. topoisomerase I d. DNA primase e. replication licensing factor
c. topoisomerase I
What would be an example of what chromatin immunoprecipitation assays (ChIPs) would identify? a. RNA interacting with the histone tails b. active enzymes c. transcription factor interacting with DNA d. methyltransferases interacting with histones
c. transcription factor interacting with DNA
All are processes that affect gene regulation by altering chromatin structure, EXCEPT a. chromatin remodeling. b. the modification of histone proteins. c. transcription factors. d. DNA methylation.
c. transcription factors.
Many antibiotics target the process of _____ because it is essential to the life of bacteria and differs significantly between bacterial and eukaryotic cells. a. replication b. RNA interference c. translation e. transcription
c. translation (A number of antibiotics bind selectively to bacterial ribosomes and inhibit specific steps in translation, but do not affect eukaryotic ribosomes.)
Retroviruses can cause cancer by which of these mechanisms?
causing the increased expression of proto-oncogenes
A technique in which neighboring genes are used to locate a gene of interest is called _____.
chromosome walking
Which best describes a cDNA library?
consists of DNA sequences that are expressed
Assuming that the rest of the genome is normal, cells with an inactivating mutation in one copy of a tumor-suppressor gene with the second copy of the gene still wild-type are most likely to_____.
continue normal divisions for this cell type
Which nucleotide base is methylated in DNA methylation?
cytosine
Sheila is experimenting with possible gene dysfunction based on its sequencing in bacterial cells. In her experiment, she creates a transcription marker that signals for an addition of five nucleotides to the RNA strand. The marker only activates when a guanine is paired with uracil. Assuming the probability of guanine pairing with uracil is 10%, what would be the total nucleotide count of the RNA molecule? Assume that the initial strand is 100 nucleotides long and that the base composition of guanine is 20%. a. 200 nucleotides b. 100 nucleotides c. 105 nucleotides d. 110 nucleotides
d. 110 nucleotides
Which rRNA component is likely to be part of a 40S ribosomal subunit? a. 23S rRNA b. 16S rRNA c. 5S rRNA d. 18S rRNA
d. 18S rRNA (Eukaryotic rRNA is produced from precursor RNA transcripts that are methylated, cleaved, and processed to produce 18S rRNA.)
Consider the image. Which represents a nucleosome? a. C b. A c. D d. B
d. B
_____ are proteins that play an important role in the body's response to infection and injury. a. PABPs b. SRs c. Histones d. Cytokines
d. Cytokines
What is an advantage of a translational control mechanism? a. It does not need mRNA to affect protein concentrations. b. It increases the amount of mRNA available in the cell. c. It does not need as much translational machinery as traditional translation. d. It allows a cell to rapidly respond to a stimulus.
d. It allows a cell to rapidly respond to a stimulus.
What is the function of lacI in the regulation of the lac operon? a. It is the operator that mediates the transcription of the structural genes. b. It encodes a repressor that, in the presence of lactose, binds to the lac operator and blocks expression of the structural genes. c. It is the promoter that mediates the transcription of the operon. d. It encodes a repressor that, in the absence of lactose, binds to the lac operator and blocks expression of the structural genes. e. It is a structural gene that encodes permease.
d. It encodes a repressor that, in the absence of lactose, binds to the lac operator and blocks expression of the structural genes.
What happens to a chromosome that loses its centromere? a. The chromosome will shorten each time the cell divides. b. Special proteins bind to this chromosome, protecting it from degradation. c. It attaches to a spindle microtubule and moves to the spindle pole. d. It will not segregate into the nucleus in mitosis and is usually lost.
d. It will not segregate into the nucleus in mitosis and is usually lost. (A chromosome lacking a centromere fails to connect to a spindle microtubule and is usually lost because it fails to move into the nucleus of a daughter cell during mitosis.)
Which of these amino acid changes could result from a mutation that changed a single base? a. Lys → Cys b. Pro → Asn c. Phe → Ser d. Phe → Leu
d. Phe → Leu (A change in the third nucleotide for a codon coding for phenylalanine (UUU or UUC), would result in leucine (UUA, UUG) being produced instead.)
Which mechanism is used by cells to regulate gene expression and to defend against certain viruses and by researchers to block expression of specific genes? a. RNA processing b. RNA editing c. RNA splicing d. RNA interference
d. RNA interference
Otis is generating RNA models for his genomics project. He is able to synthesize two RNA models with a small base pair differentiation of three base pairs. When enacting the algorithm for producing secondary structures, he saw that the configurations were different for each model. What principle of RNA is most reflected through Otis's project? a. The base pairing in RNA is a limitation to the function of the molecule. b. The stems in the structure based on its ribose sugar will determine its structure. c. The presence of uracil could dictate the function of the RNA molecule. d. RNA's degree of function will vary based on the structure it takes on.
d. RNA's degree of function will vary based on the structure it takes on.
A mutation in RNA polymerase I would likely result in which of these consequences? a. The cell would no longer be regulated in its gene expression. b. Amino acids will fail to attach during the elongation phase of transcription. c. There would remain an abundance of RNA components in the nucleus. d. The creation and functioning of ribosomes will be disrupted.
d. The creation and functioning of ribosomes will be disrupted.
Which of these statements concerning bacterial RNA polymerase is FALSE? a. Without sigma factor, RNA polymerase will initiate transcription at a primary point along DNA. b. The formation of the holoenzyme is dependent on associative binding of sigma factor. c. The alpha and beta units primarily function in the catalysis of RNA elongation through nucleotide addition. d. The omega subunit is not essential for transcription or enzyme stability.
d. The omega subunit is not essential for transcription or enzyme stability.
Which of these statements is TRUE regarding the process of transcription? a. RNA synthesis is complementary and parallel to the template strand. b. The nontemplate is usually transcribed. c. New nucleotides are added to the 3'-OH end proceeding in the 3' to 5' direction. d. The promoter dictates the first nucleotide that will be transcribed into RNA.
d. The promoter dictates the first nucleotide that will be transcribed into RNA.
What is the outcome of RNA editing? a. Translation from the edited mRNA is blocked. b. mRNA is targeted for degradation. c. Sequences of two genes are combined in the edited mRNA to code for a single protein. d. The protein translated from the edited mRNA has a sequence different from its gene. e. Introns are spliced out.
d. The protein translated from the edited mRNA has a sequence different from its gene.
Mark is a geneticist in training focused on learning the functions of RNA in an eukaryotic cell. He implements a model that targets the gene regulating photosensitivity. He compares the experimental cell with a control and finds the experimental cell is less resistant to light exposure than the control cell. Which of these statements can Mark assume is the associative factor for the difference? a. CRISPR RNAs targeted markers set by the model, causing a shift in gene expression in the process. b. There was a malfunction in the mRNA. c. The gene failed to be encoded during transcription. d. There was a modification in the function of lncRNAs.
d. There was a modification in the function of lncRNAs.
Which statement is not true about repressors in eukaryotic cells? a. They can compete with activators for DNA‑binding sites. b. They bind to silencer sequences. c. They can interfere with the assembly of the basal transcription apparatus. d. They directly block RNA polymerase. e. They can bind near an activator site and prevent activator contact with the basal transcription apparatus.
d. They directly block RNA polymerase.
What is the role of tryptophan in the regulation of the trp operon? a. When tryptophan levels are high, tryptophan binds to RNA polymerase to stimulate transcription. b. When tryptophan levels are low, tryptophan stimulates the transcription of the structural genes. c. When tryptophan levels are low, tryptophan inactivates the trp repressor. d. When tryptophan levels are high, tryptophan binds to the inactive trp repressor, making it active. e. When tryptophan levels are high, tryptophan stimulates the transcription of the trp regulatory gene.
d. When tryptophan levels are high, tryptophan binds to the inactive trp repressor, making it active.
What is the regulatory segment of an mRNA that binds a small molecule resulting in a change in the production of the protein encoded by this mRNA called? a. a repressor b. a promoter c. an activator d. a riboswitch e. an attenuator
d. a riboswitch
Which option matches the modification of histones with the correct effect on the histone? a. methylation of histones; stimulates replication b. methylation of H3K4; represses transcription c. acetylation of histones by acetyltransferase; represses transcription d. acetylation of histones; stimulates transcription e. deacetylation of histones by deacetylase; stimulates transcription
d. acetylation of histones; stimulates transcription
In eukaryotes, DNA polymerase _____ includes primase activity and initiates nuclear DNA synthesis. Please choose the correct answer from the following choices, and then select the submit answer button. a. epsilon b. gamma c. beta d. alpha
d. alpha
Which form of gene regulation primarily occurs in eukaryotes? a. regulation of mRNA stability b. All of these forms of regulation occur equally in both prokaryotes and eukaryotes. c. regulation of translation d. alteration of chromatin structure e. regulation of transcription
d. alteration of chromatin structure
What is the correct order of events in the elongation process? a. EF-Tu binds with GTP and a charged tRNA, translocation of the ribosome down the mRNA, FT-Ts recharges the EF-Tu GTP complex b. a charged tRNA binds to the P site, peptide bonds form between the amino acids that are attached to the tRNAs, translocation of the ribosome down the mRNA c. EF-G shifts the ribosome over the next codon, a charged tRNA binds to the A site, the empty tRNA is shifted to the P site d. an anticodon on a charged tRNA binds the codon on the mRNA in the A site, GTP is cleaved to form GDP, an empty tRNA shifts from the E site to the cytoplasm
d. an anticodon on a charged tRNA binds the codon on the mRNA in the A site, GTP is cleaved to form GDP, an empty tRNA shifts from the E site to the cytoplasm
Primers are synthesized where on the lagging strand of a replication fork? a. only at the 3' end of the newly synthesized strand b. only at the 5' end of the newly synthesized strand c. at multiple places within an Okazaki fragment d. at the beginning of every Okazaki fragment
d. at the beginning of every Okazaki fragment
What is an example of secondary structure? a. amino acid sequence b. two proteins interacting c. the folding of a protein back onto itself d. beta pleated sheet
d. beta pleated sheet
If Gene A is transcribed from the top strand of DNA and Gene B is transcribed from the bottom strand of DNA, then the coding sequence for Gene A is located on a. the template strand only. b. the top strand of DNA only. c. the bottom strand of DNA only. d. both strands of DNA.
d. both strands of DNA.
What transcription unit elements are included in the RNA-coding region? a. promoter b. transcription start site only c. terminator only d. both the transcription start site and the terminator
d. both the transcription start site and the terminator
How do transcription factors regulate transcription? a. by methylating cytosine bases b. by undergoing modifications c. by inhibiting transcription d. by recruiting other proteins
d. by recruiting other proteins
Sequences that possess considerable similarity between different genes are called _____ sequences. a. polymerase b. terminating c. promoting d. consensus
d. consensus (The presence of consensus in a set of nucleotides usually implies that the sequence is associated with an important function.)
Which of these mutations would likely happen first in the progression of a normal cell to a cancerous one? a. a spontaneous mutation in a gene that plays a role in metastatic invasion b. an inherited mutation in a gene encoding a structural protein c. a spontaneous mutation in a gene encoding a structural protein d. either a spontaneous mutation in a gene involved in cell division or an inherited mutation in a gene involved in cell division
d. either a spontaneous mutation in a gene involved in cell division or an inherited mutation in a gene involved in cell division
The largest and most complex mitochondrial genomes come from a. yeasts. b. mice. c. fruit flies. d. flowering plants. e. humans.
d. flowering plants.
Expression of a particular mutation in E. coli causes previously initiated replication to quickly halt and DNA ahead of the two replication forks to become highly twisted. The mutation most likely affects a gene that encodes DNA a. initiator. b. helicase. c. primase. d. gyrase.
d. gyrase.
Which item is a common DNA‑binding motif? a. alanine zipper b. loop‑helix‑loop c. iron‑finger d. helix‑turn‑helix e. ring‑loop‑ring
d. helix‑turn‑helix
All of these components are required for replication in bacterial cells, except for a. DNA polymerase III. b. DNA primase. c. DNA ligase. d. histone proteins.
d. histone proteins.
The lac operon would produce the greatest amount of β-galactosidase when a. both lactose and glucose are present. b. both lactose and glucose are absent. c. lactose is absent but glucose is present. d. lactose is present but glucose is absent.
d. lactose is present but glucose is absent. (When glucose is absent, β-galactosidase breaks down lactose into glucose to be used for energy.)
The first structural gene of the trp operon, trpE, contains a 5' UTR which is also known as a(n) _____ that has four regions. a. terminator b. initiator c. header d. leader
d. leader
What essential role is played by the NORAD lncRNA? a. prevents the miRNAs from attaching to and inhibits the translation of mRNAs b. plays a central role in dosage compensation in mammalian cells c. regulates the expression of protein-encoding genes d. maintains chromosome stability in mammalian cells
d. maintains chromosome stability in mammalian cells
Challenge this Question A stretch of 100 base pairs of DNA contains 15 complete rotations. This DNA molecule is a. negatively supercoiled. b. denatured. c. relaxed. d. positively supercoiled.
d. positively supercoiled. (his DNA molecule has more rotations per 100 bp than relaxed DNA.)
The way that proteins fold into beta pleated sheets and alpha helices is dependent on their a. quaternary structure. b. peptide bonds. c. tertiary structure. d. primary structure. e. secondary structure.
d. primary structure.
What structures affect stalling and the elongation of transcription? a. AU-rich elements b. binding sites for transcription factors c. boundary elements d. regulatory factors
d. regulatory factors
All these components are necessary for the initiation of translation in a bacterial cell, EXCEPT a. GTP. b. mRNA. c. small and large ribosomal d. subunits. d. release factor 1.
d. release factor 1. (Release factor 1 is involved with termination as opposed to initiation.)
Which of the proteins are directly responsible for ensuring that eukaryotic DNA is replicated precisely once in each round of replication, even though there are thousands of replication origins? a. initiator protein b. DNA polymerase δ c. single‑strand‑binding proteins d. replication licensing factor e. DNA primase
d. replication licensing factor
Which biological process does RNA NOT play a vital role in? a. replication b. translation c. transcription d. stable, long-term genetic information storage
d. stable, long-term genetic information storage
A transcription unit encodes all of these, EXCEPT a. promoters. b. terminators. c. RNA-coding regions. d. tRNA molecules.
d. tRNA molecules.
Which enzyme is responsible for the replication of chromosome ends in germ cells and certain proliferating somatic cells? a. DNA polymerase δ b. DNA ligase c. topoisomerase d. telomerase e. geminin
d. telomerase
What is necessary for the addition of the poly(A) tail? a. the Shine-Dalgarno sequence b. at least one intron at the end of the pre‑mRNA c. mRNA degradation enzymes d. the consensus sequence, AAUAAA e. mRNA chaperone proteins
d. the consensus sequence, AAUAAA
Mutations in which of these lac operon genes or regions are trans in their effect on the regulation of the operon? a. the lacO operator b. the lac terminator c. the lac promoter d. the lacI gene
d. the lacI gene
Which mode of replication produces two circular molecules directly? a. dispersive b. linear eukaryotic c. rolling-circle d. theta
d. theta
Ribozymes have all these capabilities, EXCEPT a. replicating RNA. b. catalyzing peptide bonds. c. splicing RNA molecules together. d. transcribing mRNA into protein.
d. transcribing mRNA into protein.
Paul is performing experiments to understand the degree of gene expression. His imaging studies of different types of motifs resulted in several graphics. Out of the images choices given, which of these motifs is paired incorrectly with its characteristics? a. helix-loop-helix: two alpha helices separated by a loop of amino acids b. leucine zipper: helix of leucine and a basic arm c. helix-turn-helix: two alpha helices d. zinc finger: two perpendicular alpha helices surrounded by four cysteine molecules
d. zinc finger: two perpendicular alpha helices surrounded by four cysteine molecules
Which of these is a practical application of molecular genetic techniques?
development of plants that are resistant to herbicides
Which is not a type of pre‑mRNA processing in eukaryotes? a. 5' cap addition b. polyadenylation c. RNA editing d. splicing e. 3' mRNA degradation
e. 3' mRNA degradation
Which of these is the first step of translation elongation? a. The small and large ribosomal subunits combine with mRNA and the tRNA carrying methionine. b. The mRNA attaches to the small ribosomal subunit. c. A peptide bond is formed between the amino acids attached to the tRNAs in the P and A sites. d. The ribosome translocates down the mRNA in the 5' -> 3' direction. e. A charged tRNA binds to the A site.
e. A charged tRNA binds to the A site.
Which is not found in a spliceosome that is actively splicing? a. protein b. small nuclear RNA c. small nuclear ribonucleoprotein particles d. Pre‑mRNA e. DNA
e. DNA
Are all eukaryotic genes colinear? a. Yes, because all genes produce protein products. b. Yes, because the order of the codons and amino acids is the same in eukaryotes. c. No, because there are often several genes that code for the same protein. d. Yes, because all codons in a eukaryotic gene are translated into a protein. e. No, because some eukaryotic genes have introns that are not translated.
e. No, because some eukaryotic genes have introns that are not translated.
There are 64 codons, 20 different amino acids, and approximately 30-50 tRNAs. Which statement does not help explain these numbers? a. Many amino acids are coded for by more than one of the 61 sense codons. b. Flexibility, or wobble, between the anticodon and the codon allows one tRNA to pair with multiple codons. c. Isoaccepting tRNAs can carry the same amino acid. d. Synonymous codons code for the same amino acid. e. The 3' base of the anticodon on the tRNA can pair weakly with the 5' codon base.
e. The 3' base of the anticodon on the tRNA can pair weakly with the 5' codon base.
Which process is based on DNA recombination? a. DNA repair b. bacterial conjugation c. homologous recombination d. crossover e. all of these
e. all of these
A mechanism of genetic regulation in which the synthesis of a short RNA is terminated before the structural genes of the operon can be transcribed is called a. negative control. b. positive control. c. repression. d. induction. e. attenuation.
e. attenuation.
A system of gene control in bacterial operons in which glucose is used preferentially and the metabolism of other sugars is repressed in the presence of glucose is called a. attenuation. b. antisense regulation. c. negative control. d. coordinate induction. e. catabolite repression.
e. catabolite repression.
Which set of conditions will lead to the highest expression of the lac structural genes? a. low levels of lactose and high levels of glucose b. high levels of the lac repressor and high levels of glucose c. low levels of lactose and low levels of glucose d. high levels of lactose and high levels of glucose e. high levels of lactose and low levels of glucose
e. high levels of lactose and low levels of glucose
A mutation in the lac promoter region that causes this region to no longer function would lead to a. expression of the lac structural genes in the absence of lactose. b. expression of the lac structural genes in the presence of lactose. c. overexpression of the lac structural genes. d. enhanced initiation of transcription of the structural genes. e. lack of expression of the lac structural genes in the presence of lactose.
e. lack of expression of the lac structural genes in the presence of lactose.
Alternative splicing produces a. genes of different lengths from the same DNA b. pre‑mRNAs of different lengths from the same DNA c. pre‑mRNAs of different lengths from the same mRNA d. mRNAs of different lengths from the same amino acid sequences e. mRNAs of different lengths from the same pre‑mRNA
e. mRNAs of different lengths from the same pre‑mRNA
A distinct clump of prokaryotic DNA observed via electron microscopy is referred to as a a. plasmid. b. nucleosome. c. nucleolus. d. nucleus. e. nucleoid.
e. nucleoid.
The discovery that some proteins are composed of more than one polypeptide chain and that different polypeptide chains are encoded by separate genes became the a. many genes, many polypeptides hypothesis. b. one protein, one polypeptide hypothesis. c. research that revealed the process of translation. d. one gene, one enzyme hypothesis. e. one gene, one polypeptide hypothesis.
e. one gene, one polypeptide hypothesis.
When mRNAs are being translated simultaneously by multiple ribosomes, the structure is known as a(n) a. polycistron. b. copolymer. c. operon. d. polytene. e. polyribosome.
e. polyribosome.
Which term describes the tertiary structural organization of chromosomal DNA that allows the long strand to be packed and fit into the cytoplasm of the cell? a. centromere b. base pairing c. telomere d. double helix e. supercoiling
e. supercoiling
Which virus is associated with cervical, penile, and vulvar cancers?
human papillomavirus (HPV)
Mutations in stimulatory genes leading to cancer typically cause the gene to be _____.
hyperactive or expressed at inappropriate times
Which treatment is NOT likely to prevent tumor growth?
inactivation of tumor-suppressor genes
Hypermethylation is thought to contribute to cancer by:
inhibiting the expression of tumor-suppressor genes.
Small DNA fragments that contain one or more restriction sites and can be attached to the end of a DNA molecule are termed _____.
linkers (Linkers are small synthetic DNA fragments that contain one or more restriction sites. Linkers can be attached to the ends of any piece of DNA.)
If the rate of clonal evolution is _____, the frequency with which mutations arise is _____.
low; low
During the cell cycle, levels of which of these will fluctuate and eventually lead to the G2 to M transition?
mitosis-promoting factor
Normal cell division proceeds at the proper speed due to _____.
signals from both stimulatory and inhibitory molecules at the same time
Aminoacyl‑tRNA synthetases recognize their specific amino acid by __________ and recognize the tRNAs that carry it by the ______________
size, charge, and R group; nucleotide sequence
A geneticist uses genetic engineering to treat patients who have an immune disorder caused by a mutation in the gene for adenosine deaminase. The geneticist removes white blood cells from the patients, transfers a functional gene for adenosine deaminase into the cells, and then infuses the treated cells back into the patient. This is an example of which type of gene therapy?
somatic gene therapy (Somatic gene therapy corrects genes only in somatic (nonreproductive) cells.)
What enzyme keeps the ends of chromosomes from shortening during the rapid cell divisions that produce tumors?
telomerase
Molecular techniques are used in:
the study of cancer, treatment of hereditary disorders, study of gene structure, and hormone creation.
Some cancers are consistently associated with the deletion of a particular part of a chromosome. Would the deleted region contain an oncogene or a tumor-suppressor gene?
tumor-suppressor
A technique for transferring protein from a gel to membrane is _____.
western blotting (Western blotting is the transfer of protein from a gel to a membrane. Here, the probe is usually an antibody, used to determine the size of a particular protein and the pattern of the protein's expression.)