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65 Cards in this Set
- Front
- Back
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Auxotrophic mutation 103 grows on minimal medium supplemented with A, B, and C; Mutation 106 grows on minimal medium supplemented with A, and C, but not B; mutation 102 grows on medium supplemented with C. What is the order of A, B, and C in a biochemical pathway?
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B --> A --> C
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What primarily determines the secondary and tertiary structures of a protein.
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The amino acid sequences ( primary structure) of the protein
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A codon is:
A. One of three nucleotides that encode an amino acid. B. Three nucleotides that encode an amino acid. C. Three amino acids that encode an amino acid. D. One of four bases in DNA. |
B. Three nucleotides that encode an amino acid.
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Through wobble, a single (Blank) can pair with more than one (Blank).
A. Codon, anticodon B. Group of three nucleotides in DNA, codon in mRNA C. tRNA, amino acid D. Anticodon, codon |
D. Anticodon, codon
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Do the initiation and terminal codons specify an amino acid? If so which one?
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The initiation codon in bacteria encodes N-formylmethionine; in eukaryotes, it encodes methionine. Termination codons do not specify amino acids.
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Amino acids bind to which part of the tRNA?
A. Anticodon B. DHU arm C. 3' End D. 5' End |
C. 3' End
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During the initiation of translation, the small ribosome binds to which consensus in bacteria?
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The Shine-Dalgarno sequences
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In elongation, the creation of peptide bonds between amino acids is catalyzed by:
A.rRNA B. Protein in the small subunit C. Protein in the large subunit D. tRNA |
A. rRNA
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In a polyribosome, the polypeptides associated with which ribosomes will be the longest?
A. Those at the 5" end of mRNA B. Those at the 3' end of mRNA C. Those in the middle of mRNA D. All polypeptides will be the same length |
B. Those at the 3' end of mRNA
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What is a constitutive gene?
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A gene that is not regulated and is expressed continually.
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Why is transcription a particularly important level of gene regulation in both bacteria and eukaryotes?
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It's the 1st step in the process of information transfer from DNA to protein. For cellular efficiency, gene expression is often regulated early in the process of protein production.
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How do amino acids in DNA-binding proteins interact with DNA?
A. By forming covalent bonds with DNA bases B. By forming hydrogen bonds with DNA bases C. By forming covalent bonds with DNA sugars |
B. By forming hydrogen bonds with DNA bases
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What is the difference between a structural and a regulatory gene?
A. Structural genes are transcribed into mRNA, but regulator genes aren't B. Structural genes have complex structure; a regulator genes have simple structure C. Structural genes encodes proteins that function in the structure of the cell; regulatory genes carry out metabolic reactions D. Structural genes encode proteins; regulatory genes control the transcription of structural genes. |
D. Structural genes encode proteins; regulatory genes control the transcription of structural genes.
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In a negative repressible operon, the regulatory protein is synthesized as an:
A. Active activator B. Inactive activator C. Active repressor D. Inactive repressor |
D. Inactive repressor
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In the presence of allolactose, the lac repressor:
A. Binds the operator B. Binds the promotor C. cannot bind to the operator D. Binds to the regulator gene |
C. cannot bind to the operator
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What is the effect of high levels of glucose on the lac operon?
A.Transcription is stimulated B. Little transcription takes place C. Transcription is not affected D. Transcription may be stimulated or inhibited, depending on the levels of lactose |
B. Little transcription takes place
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T/F All genetic mutations that arise in a genome affect thestructure of a protein.
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FALSE
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Which of the following statements is correct aboutisoaccepting tRNAs?
A. Isoaccepting tRNAs can switch whichamino acids that they typically bind to. B. Isoaccepting tRNAs have differentanticodons. C Two synonymous codons specify differentisoaccepting tRNAs. D. Both A and B. E. Both B and C. |
E. Both B and C.
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Which statement is true regarding the binding of an aminoacid to a tRNA?
A. Amino acids bind to the 5’ end of the tRNA. B. The binding of amino acids to tRNAs requiresGTP. C. There is one aminoacyl tRNA synthetase foreach of the 20 amino acids. D. Each aminoacyl tRNA synthetase recognizes adifferent tRNA. E. Both c and d.
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C. There is one aminoacyl tRNA synthetase for each of the 20 amino acids.
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Protein synthesis is energy-requiring. For every cycleof elongation (addition of one amino acid) that takesplace in a bacterial cell_____ is/are hydrolyzed.
A. 1 ATP for charging of the tRNA B. 1 GTP for peptide bond formation to occur C. 2 GTP, one for peptide bond formation and one forribosome translocation to occur D. 1 ATP and 2 GTP (because all of the above areneeded) |
D. 1 ATP and 2 GTP (because all of the above are needed)
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mRNA editing in eukaryotes would be what form ofgene expression regulation?
A. Post-transcriptional regulation B. Transcriptional regulation C. Post-translational regulation D. None of the above |
A. Post-transcriptional regulation
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Whattype of operon is the lac operon?
A. Positive inducible operon B. Positive repressible operon C. Negative inducible operon D. Negative repressible operon |
C. Negative inducible operon
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Mutations in which of the following DNA sequencesare only cis-acting?
A. Structural gene sequence mutations B. Operator and promoter DNA mutations C. Regulatory gene sequence mutations D. None of the above |
B. Operator and promoter DNA mutations
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Consider the following partial diploid strain of E. coli:lacI+ lacO+ lacZ+ lacY- / lacIS lacOclacZ- lacY+Under what conditions will this strain make functional bgalactosidase?
A. only when lactose is present B. constitutively C. Never, once the superrepressor binds. |
C. Never, once the superrepressor binds.
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What is the function of deacetylase enzymes?
A. To add acetyl groups to amino acids B. To replace acetyl groups on amino acids withmethyl groups C. To remove acetyl groups from amino acids D. To remove methyl groups from amino acids andreplace them with acetyl groups14 |
C. To remove acetyl groups from amino acids
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In eukaryotic cells, genes that are coordinately activated bya particular stimulus generally:
A. Are physically clustered in the same operon.B. Have short regulatory sequences in common in theirpromotor regions. C. Are activated by the same transcriptional activators D. Both B and C E. All of the above |
D. Both B and C
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Suppose that a mutant form of GAL80 protein lacks thedomain that binds to GAL4 protein. Yeast cells with thismutant GAL80 will:
A. never activate the genes needed for galactosemetabolism. B. always repress the genes needed for galactosemetabolism even in the presence of galactose. C. always activate the genes needed for galactosemetabolism even in the absence of galactose. |
C. always activate the genes needed for galactose metabolism even in the absence of galactose.
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What would the be the result on sex determination inDrosophila if a mutation removed the upstream 3’splice site so that only the downstream splice siteremained?
A. All the flies would be female B. All the flies would have intersex phenotypesC. All the flies would be male D. None of the above |
A. All the flies would be female
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In eukaryotes, there are a variety of post-transcriptionalmechanisms of gene regulation. Which of the mechanismsbelow is a post-transcriptional mechanism that acts in thenucleus?
A. alternative splicing of pre-mRNA B. increased initiation of translation C. miRNA-mediated translational repression D. addition of phosphate or sugar groups toproteins |
A. alternative splicing of pre-mRNA
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Identify the following type of mutation:
Original coding DNA: AGT TGT AAC GCG ACCOriginal AA Sequence: Ser- Cys - Asn - Ala - Thr Mutant coding DNA: AGT TAT AAC GCG AACMutant AA Sequence: Ser- Tyr - Asn - Ala – Thr A. Missense mutation B. Nonsense mutation C. Silent mutation D. Frameshift mutation |
A. Missense mutation
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A mutation in gene X overrides the effect of a previousmutation in the gene and restores wild-type phenotype.The second mutation in gene X occurred at the same locusas the first mutation. This type of mutation is called a(n):
A. reverse mutation. B. intragenic suppressor mutation. C. intergenic suppressor mutation. D. neutral mutation. E. forward mutation. |
a. reverse mutation.
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A(n) _______ error occurs when a mismatched base hasbeen incorporated into a newly synthesized nucleotidechain. When this DNA is copied, this error leads to a(n)_____ error.
A. replicated; incorporated B. deamination; replicated C. incorporated; replicated D. incorporated; deamination E. Strand slippage; incorporated |
C. incorporated; replicated
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Which of the following characterizes the mode oftransposition of retrotransposons?
A. It involves an RNA intermediate. B. It involves the initial synthesis of transposase. C. It involves the production of a protein repressor. D. It only occurs in nondividing host genomes. |
A. It involves an RNA intermediate.
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Which is NOT required for PCR?
A. DNA polymerase B. all four nucleotides C. template DNA D. DNA ligase E. primers |
D. DNA ligase
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When present in small amounts in sequencing reactions,dideoxyribonucleoside triphosphates (ddNTPs) terminate thesequencing reaction at different positions in the growing DNAstrands. ddNTPs stop a sequencing reaction because they:
A. lack a 5′ phosphate group. B. have a hydroxyl (-OH) group at their 5′ position. C. lack a hydroxyl (–OH) group at their 3′ position. D. permanently bind to the active site of DNApolymerase. E. cause DNA polymerase to fall off the template strand. |
C. lack a hydroxyl (–OH) group at their 3′ position.
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Suppose that pumpkin weight is controlled by unlinked loci,each with two segregating alleles that have additive effects.How many loci are likely involved with the determination ofpumpkin weight if one of the 1024 F2 offspring from a crossof homozygous parents has a parental phenotype?
A. 2 loci are involved B. 3 loci are involved C. 4 loci are involved D. 5 loci are involved E. 6 loci are involved |
D. 5 loci are involved
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Which of the following mapping methods has the lowestresolution?
A. recombination frequency B. restriction mapping C. DNA sequencing D. sequence-tagged site (STS) mapping E. All of the above have similar levels of resolution. |
A. recombination frequency
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The human genome contains three genes for enolase (a, b,g), whereas yeast contains just one gene for enolase. Thethree human enolase genes are __________ of each other,whereas the human and yeast enolase genes are__________ of each other.
A. allelic variants; homologs B. orthologs; paralogs C. paralogs; orthologs D. orthologs; homologs E. identical twins; distant relatives |
C. paralogs; orthologs
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If you were interested in learning which proteins interactwith the protein you are studying, which technique wouldbe most useful?
A. affinity capture B. protein sequence BLAST C. mass spectrometry D. Liquid chromatography E. All of the above. |
A. affinity capture
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If a trait in a population is regulated by one locus, andall of the individuals in the population have the samegenotype, what is the broad-sense heritability of thistrait in that population?
A. Indeterminate B. Heritability = 0 C. Heritability = 1 D. Heritability = 2 |
B. Heritability = 0
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What is the response to selection for milk production ina population of cows in which the narrow-senseheritability is 0.5, the mean milk production of the herdis 60 liters per week, and the mean milk production ofthe parents is 80 liters per week?
A. R= -10 liters B. R = 0 liters C. R = 10 liters D. R = 20 liters |
C. R = 10 liters
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In the trp operon, what happens to the trp repressor in the absence of tryptyphan:
A. It binds to the operator and represses transcription. B. It cannot bind to the operator and transcription takes place C. It binds to the regulator gene and represses transcription D. It cannot bind to the regulator gene and transcription takes place |
B. It cannot bind to the operator and transcription takes place
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Attenuation results when which regions of the 5' UTR pair?
A. 1 and 3 B. 2 and 3 C. 2 and 4 D. 3 and 4 |
D. 3 and 4
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What are some different processes that affect gene regulation by altering chromatin structure?
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Three general processes are chromatin remodeling, the modification of histone proteins (e.g. methylation and acetylation of histones) and DNA methylation
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Most transcriptional activator proteins affect transcription by interacting with?
A. Intons B. The basal transcription apparatus C. DNA polymerase D. The terminator |
B. The basal transcription apparatus
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The amino acid sequence Met-Trp-His can be encoded by the DNA template sequence
A. 3'-TACACCGTA-5'. B. 5'-TACACCGTA-3'. C. 3'-TACACCGTG-5'. D. 5'-TACACCGTG-3'. E. Both A and C are correct. |
E. Both A and C are correct.
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The genetic code is said to be degenerate, which means:
A. more than one codon can specify an amino acid. B. more than one amino acid can specify a codon. C. the start codon is almost always the same, AUG. D. None of the above |
A. more than one codon can specify an amino acid.
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Mutations that introduce stop codons cause a number of genetic diseases. For example, from 2% to 5% of the people who have cystic fibrosis possess a mutation that causes a premature stop codon in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR). This premature stop codon produces a truncated form of CFTR that is nonfunctional and results in the symptoms of cystic fibrosis. One possible way to treat people with genetic diseases caused by these types of mutations is to trick the ribosome into reading through the stop codon, inserting an amino acid into its place. Although the protein produced may have one altered amino acid, it is more likely to be at least partly functional than is the truncated protein produced when the ribosome stalls at the stop codon. Indeed, geneticists have conducted clinical trials on people with cystic fibrosis with the use of a drug called PTC124, which interferes with the ribosome's ability to correctly read stop codons (C. Ainsworth, 2005, Nature 438:726–728). On the basis of what you know about the mechanism of nonsense-mediated mRNA decay (NMD), would you expect NMD to be a problem with this type of treatment?
A. Yes, NMD would be a problem because even although the ribosome would read through the stop codon, premature degradation of the mRNA would still take place. B. No, NMD would not be a problem because it only occurs in prokaryotes. C. Yes, NMD would be a problem, as it requires ribosome to recognize a specific stop codon. D. No, NMD would not be a problem because the ribosome would read through the mutated stop codon, removing all of the exon-junction proteins on the mRNA that would normally signal premature degradation of that mRNA. |
D. No, NMD would not be a problem because the ribosome would read through the mutated stop codon, removing all of the exon-junction proteins on the mRNA that would normally signal premature degradation of that mRNA.
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Your lab supervisor has translated an mRNA in vitro (in a test tube) that results in the amino acid sequence Met-Pro-Ile-Ser-Ala. You try to repeat this experiment but you forget to add GTP to the reaction mixture. What results do you expect from your experiment?
A. translation occurs but with a decrease in the amount of protein produced. B. the Met is delivered to the ribosome-mRNA but no further amino acids are added. C. you have the same result as your supervisor. D. no translation occurs. |
D. no translation occurs.
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tRNA molecules that accept the same amino acids yet have different anticodons are referred to as
A. isometric tRNAs. B. Wobble tRNAs. C. isoaccepting tRNAs. D. redundant tRNAs. |
C. isoaccepting tRNAs.
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MicroRNAs are small RNA molecules that bind to the 3' UTR of mRNAs and suppress translation. The mechanism by which miRNAs prevent mRNA translation is incompletely understood, but as we learn more about the initiation of translation in eukaryotes, we can develop better hypotheses for this silencing process. Using your understanding of translation in eukaryotes, which of the following hypotheses most likely describes how miRNA binding could suppress translation of the mRNA?
A. miRNA most likely binds to the 3' end of the mRNA and prevents the binding of the poly-A tail proteins that help the ribosome bind at the 5' end. B. miRNA most likely prevents the translation of the proteins that bind to the 5' cap to help initiate translation. C. miRNA most likely directly blocks the ribosome from moving along the mRNA, causing it to stall near the 5' end of the mRNA. D. miRNA most likely directly blocks the large subunit of the ribosome from binding to the small subunit of the ribosome on the mRNA. |
A. miRNA most likely binds to the 3' end of the mRNA and prevents the binding of the poly-A tail proteins that help the ribosome bind at the 5' end.
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The following event(s) contribute to the termination of translation:
A. A ribosome encounters a termination codon. B. RF1 or RF2 binds the A site of the ribosome. C. The Kozak sequence is bound by the ribosome. D. A, B, and C are correct. E. A and B are correct. |
E. A and B are correct.
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Which of the following stages of translation does NOT depend on base pairing?
A. charging of tRNA molecules B. initiation C. elongation D. A and B |
A. charging of tRNA molecules
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In a repressible operon under negative control, the protein produced by the regulator gene will be synthesized as an
A. inactive activator. B. active activator. C. active repressor. D. inactive repressor. |
D. inactive repressor.
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An operon that is normally transcriptionally active and must be turned off is called a(n)
A. repressible operon. B. inducible operon. C. a constitutive operon. D. positive control operon. E. activator operon. |
A. repressible operon.
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Which of the following correctly outlines the role of alternative splicing in the control of sex differentiation in Drosophila?
A. Alternative splicing allows male flies to produce sperm with either an X or a Y chromosome, causing sex differentiation. B. Alternative splicing generates a functional Tra protein in males and a non-functional Tra protein in females, which affects sex development. C. Alternative splicing early in embryonic development allows males and females to produce distinct products from the same genes, leading to flies with either male or female sex characteristics. D. Alternative splicing does not contribute to sex differentiation in flies. |
C. Alternative splicing early in embryonic development allows males and females to produce distinct products from the same genes, leading to flies with either male or female sex characteristics.
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A mutation at the operator site of an inducible operon prevents the repressor protein from binding. This will result in:
A. no change in the operon's activity. B. an increase in the intracellular level of cAMP. C. an operon that is always transcriptionally active. D. an operon that is always inactive. |
C. an operon that is always transcriptionally active.
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RNA interference can repress proteins by all of the following mechanisms EXCEPT:
A. promoting histone or DNA methylation. B. promoting mRNA degradation. C. blocking translation. D. promoting histone acetylation. |
D. promoting histone acetylation
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Eukaryotic gene expression is different from prokaryotic expression in which of the following ways?
A. Eukaryotes have operons. B. Prokaryotic DNA associates with histones. C. Eukaryotic DNA forms chromatin. D. Prokaryotes export mRNA from the nucleus. E. None of the above. |
C. Eukaryotic DNA forms chromatin.
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Malaria, one of the most pervasive and destructive of all infectious diseases, is caused by Plasmodium parasites that are transmitted via mosquitoes. Plasmodiumparasites are able to evade the host immune system by constantly altering the expression of their var genes, which encode Plasmodium surface antigens (L. H. Freitas-Junior et al., 2005, Cell 121:25–36). In this way, the immune system can never identify the cells that belong to the Plasmodium parasites in order to eliminate them from the body. Individual var genes are expressed when chromatin structure is disrupted by chemical changes in histone proteins. What type of chemical changes in the histone proteins might be responsible for these changes in gene expression?
A. Removal of the histone tails from the histones by proteolytic enzymes. B. Addition or removal of acetyl or methyl groups to/from the histone tails. C. Removal of all of the acidic amino acids from the histones. D. All of the above are histone modifications that the Plasmodium parasites would likely use to influence expression of the var genes. |
B. Addition or removal of acetyl or methyl groups to/from the histone tails.
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What is an insulator?
A. A transcriptional repressor protein that surrounds the telomeres and centromeres B. A segment of DNA that forms supercoiled heterochromatin and which is devoid of any binding sites for regulator proteins C. A sequence of DNA that inhibits the action of enhancers in a position-dependent manner D. A special type of histone that occurs at the boundaries of genes E. A protein that blocks RNA polymerase from interacting with a promoter |
C. A sequence of DNA that inhibits the action of enhancers in a position-dependent manner
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Which of the following E. coli strains with the lac genotypes will synthesize normal levels of β-galactosidase (encoded by lacZ) in the presence of lactose?
A. lacIs lacP+ lacO+ lacZ+ lacY–/lacI+ lacP+ lacO+ lacZ– lacY+ B. lacI+ lacP+ lacO+ lacZ+ lacY+ C. lacI– lacP– lacO– lacZ– lacY– D. lacI– lacP– lacO+ lacZ+ lacY+ |
B. lacI+ lacP+ lacO+ lacZ+ lacY+
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Changes in chromatin structure that support activation of transcription in eukaryotes include:
A. sliding of nucleosomes to make regions of the DNA accessible. B. removal of acetyl groups from histone proteins C. Removal of methyl groups from cytosine bases within the DNA D. A and C. E. All of the above. |
C. Removal of methyl groups from cytosine bases within the DNA
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A mutant strain of E. coli produces β-galactosidase (encoded by the lacZ gene) in the presence and in the absence of lactose. Which of the following mutations will cause this result? Note that this strain of E. coli is not a partial diploid.
A. Mutations in the lac operator that prevent the regulatory proteins from binding the DNA. B. Mutations in the lacI gene that encodes the repressor protein. C. Mutations in the CAP binding site that prevent CAP from binding the DNA. D. Both A and B are correct. E. All of the above are correct. |
D. Both A and B are correct.
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A geneticist is trying to determine how many genes are found in a 300,000-bp region of DNA. Analysis shows that the DNA is heavily methylated in four different regions of this piece of DNA. What might these modifications suggest about the number of genes located in this DNA segment?
A. There are fewer than two genes in this region. B. There can only be one gene in this region. C. There are at least four genes in this region. D. There are at least eight genes are in this region. |
C. There are at least four genes in this region.
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