2024 BIOS252 Biology Comprehension Exam With Answers (226 Solved Questions)

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VERSION 3Which term would be applied to a regulatory condition that occurs when protein is associated witha particular section of DNA and greatly reduces transcription? - negative controlIn the diagram below, what type of control, positive or negative, is operating?-{ }( )-|-structrual gene-^{regulatory protien}makes a transcription. - positive controlT/F Under a system of positive control, transcription does not occur unless a regulator moleculedirectly stimulates RNA production. - TrueT/F Under a system of negative control, genetic expression occurs unless some form of regulatorshuts off such expression. - TrueWhich term is used to describe enzymes that are produced only when specific substrates arepresent in the environment? - inducible: This term best describes enzymes that are producedonly when specific substrates are present in the environment to induce their production.Which term refers to a contiguous genetic complex that is under coordinated control? - operonThings to define - allostericlysogenattenuationprototrophoperonCryan experiments with gut microbes16 interaction

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17 interactionWhich of the following mutations could lead to constitutive expression of the genes of the lacoperon? - A mutation in the operator sequence. Such a mutation could prevent binding of therepressor, allowing expression under all conditions.Which of the following best describes the biological role of the lac operon? - It ensures that a celldedicates resources to the production of enzymes involved in lactose metabolism only whenlactose is available in the environment. The cell expends energy to produce the proteinsnecessary for lactose metabolism only when lactose is present.T/F The placement of the operator sequence between the promotor and the structural genes iscritical to the proper function of the lac operon. - True. When the repressor binds to theoperator, RNA polymerase cannot transcribe the structural genes.In the lac operon, the product of structural gene lacZ is capable of ________. - splitting theβ-linkage of lactoseWhich term most appropriately refers to a regulatory protein in prokaryotes? - DNA bindingproteinA constitutive mutation in the lac operon may be of several types. Name two types of constitutivemutations. - lacOc, lacI-T/F Regarding the lactose utilization system in E. coli, a constitutive mutant is one in which thethree enzymes are produced regardless of the presence or absence of lactose. - TrueWhich of the following is a neurochemical microbes in our gut can make? - GABAExperiments led by Cryan's group found that - Mice fed lactobacilllus were more calm,behaviorally, when measured via a 6 minutes swim test.When Lyte asked, "Can bacteria cause stress in mice?" he did an experiment that measured: -how mice approached ledges of a mazeT/F Dr. Lyte's inital experiments linking the microbiome to behavior were immediately ground-breaking and game-changing for the field. - False

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Which of the following terms best characterizes catabolite repression associated with the lacoperon in E. coli? - positive controlT/F Lactose is an inducer of the lac operon. - True. Lactose indirectly induces or stimulates thetranscription of genes involved in its metabolism.What would be the effect of a mutation in the lacI gene that prevented the repressor from bindingto lactose? - The lac Z, Y, and A genes would not be expressed. If lactose could not bind to therepressor, the repressor would stay bound to the operator and repress the transcription of thelac Z, Y, and A genes.What is the role of glucose in catabolite repression? - It decreases the levels of cAMP in the cell,repressing transcription from the lac operon.Glucose decreases the levels of cAMP in the cell,preventing formation of the CAP-cAMP complexes necessary for the stimulation of transcriptionfrom the lac operon.For the genotype,I + O+ Z+/ F' I - O+ Z+which of the following should be entered into the chart?GenotypeI + O+ Z+/ F' I - O+ Z+I - Oc Z+/ F'I - O+ Z-I s Oc Z+/ F'I + O+ Z+I - O+ Z+/ F' I - O+ Z+I+ = wild-type repressorI- = mutant repressor (unable to bind to the operator)Is = mutant repressor (insensitive to lactose)O+ = wild-type operatorOc = constitutive operator (insensitive to repressor)lactose or no lactose in chart - - + (beta gal made when there is lactose)For the genotype,I - Oc Z+/ F'I - O+ Z-which of the following should be entered into the chart?Genotype

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I + O+ Z+/ F' I - O+ Z+I - Oc Z+/ F'I - O+ Z-I s Oc Z+/ F'I + O+ Z+I - O+ Z+/ F' I - O+ Z+I+ = wild-type repressorI- = mutant repressor (unable to bind to the operator)Is = mutant repressor (insensitive to lactose)O+ = wild-type operatorOc = constitutive operator (insensitive to repressor)lactose or no lactose in chart - + +For the genotype,I s Oc Z+/ F'I + O+ Z+which of the following should be entered into the chart?GenotypeI + O+ Z+/ F' I - O+ Z+I - Oc Z+/ F'I - O+ Z-I s Oc Z+/ F'I + O+ Z+I - O+ Z+/ F' I - O+ Z+I+ = wild-type repressorI- = mutant repressor (unable to bind to the operator)Is = mutant repressor (insensitive to lactose)O+ = wild-type operatorOc = constitutive operator (insensitive to repressor)lactose or no lactose in chart - + +For the genotype,I - O+ Z+/ F' I - O+ Z+which of the following should be entered into the chart?GenotypeI + O+ Z+/ F' I - O+ Z+I - Oc Z+/ F'I - O+ Z-I s Oc Z+/ F'I + O+ Z+I - O+ Z+/ F' I - O+ Z+

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I+ = wild-type repressorI- = mutant repressor (unable to bind to the operator)Is = mutant repressor (insensitive to lactose)O+ = wild-type operatorOc = constitutive operator (insensitive to repressor)lactose or no lactose in chart - + +Predict the level of genetic activity of the lac operon as well as the status of the lac repressorand the CAP protein under the cellular conditions listed in the accompanying table.Line Lactose Glucose(a) - -(b) + -(c) - +(d) + +line a: - The repressor is bound to the operator, and CAP is bound to its binding site. The operon isnot transcribed.Predict the level of genetic activity of the lac operon as well as the status of the lac repressorand the CAP protein under the cellular conditions listed in the accompanying table.Line Lactose Glucose(a) - -(b) + -(c) - +(d) + +line b: - The repressor is inactive, and CAP is bound to its binding site. The operon is beingtranscribed at a high level.Predict the level of genetic activity of the lac operon as well as the status of the lac repressorand the CAP protein under the cellular conditions listed in the accompanying table.Line Lactose Glucose(a) - -(b) + -(c) - +(d) + +

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line c: - The repressor is bound to the operator, and CAP is not bound to its binding site. Theoperon is not transcribed.Predict the level of genetic activity of the lac operon as well as the status of the lac repressorand the CAP protein under the cellular conditions listed in the accompanying table.Line Lactose Glucose(a) - -(b) + -(c) - +(d) + +line d: - The repressor is inactive, and CAP is not bound to its binding site. The operon istranscribed at a low level.T/F In general, one could say that there are fewer levels of regulation possible in prokaryotesthan in eukaryotes. - TrueRegarding eukaryotic and prokaryotic genetic regulation, what process seems to be the mostsimilar between the two? - transcriptional regulationIs the binding of a transcription factor to its DNA recognition sequence necessary and sufficientfor an initiation of transcription at a regulated gene?What else plays a role in this process? - Transcription factors are proteins that are necessaryfor the initiation of transcription. However, they are not sufficient for the initiation oftranscription. Transcription factors contain at least two functional domains: one binds to the DNAsequences of promoters and/or enhancers, while the other interacts with RNA polymerase orother transcription factors.What is the role of Dicer in RNA-induced gene silencing? - It cleaves longer RNAs into short,regulatory RNA molecules. The regulatory siRNAs and miRNAs are involved in suppression of geneexpression.T/F Alternative splicing of single mRNA transcripts gives rise to multiple mRNAs. - True.Alternative splicing of mRNA transcripts is a process used to regulate gene expressionposttranscriptionally.Pro or Eu:

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adapted to challenges of a single-celled existence, rapid turnover of mRNA, translation can occurimmediately after mRNA is transcribed,cis-acting regulatory proteins required for transcriptioninitiation, regulation of expression occurs at many checkpoints, chromatin remodeling requiredfor expression of many genes, introns in genes must be spliced out before mRNA is mature, mostorganisms optimized for a multicellular lifestyle, DNA found in nucleus requires transport acrossmembranem, RNAs have various half-lives - Pro: adapted to challenges of a single-celledexistence, rapid turnover of mRNA, translation can occur immediately after mRNA is transcribedEu:cis-acting regulatory proteins required for transcription initiation, regulation of expressionoccurs at many checkpoints, chromatin remodeling required for expression of many genes,introns in genes must be spliced out before mRNA is mature, most organisms optimized for amulticellular lifestyleDNA found in nucleus requires transport across membrane, mRNAs havevarious half-lives__________________ refers to changes in DNA/chromosome structure that can influence overallgene output - chromatin remodeling_________ are sequences in DNA to which transcription factors and RNA polymerase bind toinitiate transcription - promoters____________ are cis- acting DNA sequences to which transcription factors bind to regulatetranscription. They can act over distances of thousands of base pairs and can be upstream,downstream, or internal to the gene they affect. - enhancerscis- acting vs trans factors -_____________ bind DNA and regulate transcription - transcription factorThe addition of a 5' cap and a poly A tail and removal of introns are all steps in_________________ - RNA processing and transportRNA processing contributes to ________________, which regulates translation - mRNA stabilityWhich of the following clusters of terms applies when addressing enhancers as elementsassociated with eukaryotic genetic regulation? - cis-acting, variable orientation, variable position

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T/F Alternative RNA processing can result in different mRNAs that start with different exons. -TrueT/F Transcription in eukaryotes is generally influenced by enhancers, just as in prokaryotes. -FalseT/F Alternative RNA processing generates different mRNAs that can direct the synthesis ofdifferent polypeptides. - TrueWhat are transcription factors? - regulatory proteins that bind to specific DNA sequences.Transcription factors are proteins that bind to specific DNA recognition sequences in thepromoter or enhancer elements of a gene.Promoters vs. Enhancers:may influence the expression of more than one gene, position can be upstream, downstream, orwithin the gene,not required for basal-level transcription, responsible for tissue- and time-specific gene expression,always upstream of the gene within 100 bases of the transcriptioninitiation site, TATA, CAAT, GC boxes, required for basal-level transcription - Promoters:may influence the expression of more than one gene, position can be upstream, downstream, orwithin the gene,not required for basal-level transcription, responsible for tissue- and time-specific gene expressionEnhancers:always upstream of the gene within 100 bases of the transcription initiation site, TATA, CAAT, GCboxes, required for basal-level transcriptionT/F Transcriptionally inactive regions of the genome are typically heavily methylated. - True.Methylation of cytosine residues is often associated with decreased transcription levels.Mutagenic studies of the promoter region of theβ-globin gene indicate that mutations in someareas are more likely than mutations in other areas to affect transcription rates. When mutationsoccur in consensus sequences (modular elements such as GC box, CAAT box, TATA box), doestranscription increase or decrease? - decreaseFor the genotype,I + O+ Z+/ F' I + O+ Z+which of the following should be entered into the chart?

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GenotypeI + O+ Z+/ F' I + O+ Z+I - Oc Z-/ F' I- Oc Z-I - Oc Z+/ F' I - O+ Z+I s Oc Z-/ F' I s O+ Z+I + = wild-type repressorI- = mutant repressor (unable to bind to the operator)Is = mutant repressor (insensitive to lactose)O+ = wild-type operatorOc = constitutive operator (insensitive to repressor)No Lactose/Lactose - - + (beta-gal made only when there is lactose)For the genotype,I- Oc Z-/ F' I- Oc Z-which of the following should be entered into the chart?GenotypeI + O+ Z+/ F' I + O+ Z+I - Oc Z-/ F' I- Oc Z-I - Oc Z+/ F' I - O+ Z+I s Oc Z-/ F' I s O+ Z+I + = wild-type repressorI- = mutant repressor (unable to bind to the operator)Is = mutant repressor (insensitive to lactose)O+ = wild-type operatorOc = constitutive operator (insensitive to repressor)No Lactose/Lactose - - -For the genotype,I- Oc Z+/ F' I - O+ Z+which of the following should be entered into the chart?GenotypeI + O+ Z+/ F' I + O+ Z+I - Oc Z-/ F' I- Oc Z-

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