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

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    VERSION 3 Which term would be applied to a regulatory condition that occurs when protein is associated with a particular section of DNA and greatly reduces transcription? - negative control In the diagram below, what type of control, positive or negative, is operating? -{ }( )-|-structrual gene- ^ {regulatory protien} makes a transcription. - positive control T/F Under a system of positive control, transcription does not occur unless a regulator molecule directly stimulates RNA production. - True T/F Under a system of negative control, genetic expression occurs unless some form of regulator shuts off such expression. - True Which term is used to describe enzymes that are produced only when specific substrates are present in the environment? - inducible: This term best describes enzymes that are produced only 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? - operon Things to define - allosteric lysogen attenuation prototroph operon Cryan experiments with gut microbes 16 interaction

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    17 interaction Which of the following mutations could lead to constitutive expression of the genes of the lac operon? - A mutation in the operator sequence. Such a mutation could prevent binding of the repressor, allowing expression under all conditions. Which of the following best describes the biological role of the lac operon? - It ensures that a cell dedicates resources to the production of enzymes involved in lactose metabolism only when lactose is available in the environment. The cell expends energy to produce the proteins necessary for lactose metabolism only when lactose is present. T/F The placement of the operator sequence between the promotor and the structural genes is critical to the proper function of the lac operon. - True. When the repressor binds to the operator, RNA polymerase cannot transcribe the structural genes. In the lac operon, the product of structural gene lacZ is capable of ________. - splitting the β - linkage of lactose Which term most appropriately refers to a regulatory protein in prokaryotes? - DNA binding protein A constitutive mutation in the lac operon may be of several types. Name two types of constitutive mutations. - lacOc, lacI- T/F Regarding the lactose utilization system in E. coli, a constitutive mutant is one in which the three enzymes are produced regardless of the presence or absence of lactose. - True Which of the following is a neurochemical microbes in our gut can make? - GABA Experiments 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 maze T/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 lac operon in E. coli? - positive control T/F Lactose is an inducer of the lac operon. - True. Lactose indirectly induces or stimulates the transcription of genes involved in its metabolism. What would be the effect of a mutation in the lacI gene that prevented the repressor from binding to lactose? - The lac Z, Y, and A genes would not be expressed. If lactose could not bind to the repressor, the repressor would stay bound to the operator and repress the transcription of the lac 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 transcription from the lac operon. For the genotype, I + O+ Z+/ F' I - O+ Z+ which of the following should be entered into the chart? Genotype 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 repressor I- = mutant repressor (unable to bind to the operator) Is = mutant repressor (insensitive to lactose) O+ = wild-type operator Oc = 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 repressor I- = mutant repressor (unable to bind to the operator) Is = mutant repressor (insensitive to lactose) O+ = wild-type operator Oc = 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? Genotype 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 repressor I- = mutant repressor (unable to bind to the operator) Is = mutant repressor (insensitive to lactose) O+ = wild-type operator Oc = 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? Genotype 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+

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    I+ = wild-type repressor I- = mutant repressor (unable to bind to the operator) Is = mutant repressor (insensitive to lactose) O+ = wild-type operator Oc = 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 repressor and 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 is not transcribed. Predict the level of genetic activity of the lac operon as well as the status of the lac repressor and 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 being transcribed at a high level. Predict the level of genetic activity of the lac operon as well as the status of the lac repressor and 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. The operon is not transcribed. Predict the level of genetic activity of the lac operon as well as the status of the lac repressor and 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 is transcribed at a low level. T/F In general, one could say that there are fewer levels of regulation possible in prokaryotes than in eukaryotes. - True Regarding eukaryotic and prokaryotic genetic regulation, what process seems to be the most similar between the two? - transcriptional regulation Is the binding of a transcription factor to its DNA recognition sequence necessary and sufficient for an initiation of transcription at a regulated gene? What else plays a role in this process? - Transcription factors are proteins that are necessary for the initiation of transcription. However, they are not sufficient for the initiation of transcription. Transcription factors contain at least two functional domains: one binds to the DNA sequences of promoters and/or enhancers, while the other interacts with RNA polymerase or other 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 gene expression. 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 expression posttranscriptionally. Pro or Eu:

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    adapted to challenges of a single-celled existence, rapid turnover of mRNA, translation can occur immediately after mRNA is transcribed,cis-acting regulatory proteins required for transcription initiation, regulation of expression occurs 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 a multicellular lifestyle, DNA found in nucleus requires transport across membranem, RNAs have various half-lives - Pro: adapted to challenges of a single-celled existence, rapid turnover of mRNA, translation can occur immediately after mRNA is transcribed Eu: cis-acting regulatory proteins required for transcription initiation, regulation of expression occurs 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 a multicellular lifestyleDNA found in nucleus requires transport across membrane, mRNAs have various half-lives __________________ refers to changes in DNA/chromosome structure that can influence overall gene output - chromatin remodeling _________ are sequences in DNA to which transcription factors and RNA polymerase bind to initiate transcription - promoters ____________ are cis- acting DNA sequences to which transcription factors bind to regulate transcription. They can act over distances of thousands of base pairs and can be upstream, downstream, or internal to the gene they affect. - enhancers cis- acting vs trans factors - _____________ bind DNA and regulate transcription - transcription factor The addition of a 5' cap and a poly A tail and removal of introns are all steps in _________________ - RNA processing and transport RNA processing contributes to ________________, which regulates translation - mRNA stability Which of the following clusters of terms applies when addressing enhancers as elements associated 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. - True T/F Transcription in eukaryotes is generally influenced by enhancers, just as in prokaryotes. - False T/F Alternative RNA processing generates different mRNAs that can direct the synthesis of different polypeptides. - True What are transcription factors? - regulatory proteins that bind to specific DNA sequences. Transcription factors are proteins that bind to specific DNA recognition sequences in the promoter or enhancer elements of a gene. Promoters vs. Enhancers: may influence the expression of more than one gene, position can be upstream, downstream, or within 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 transcription initiation 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, or within the gene,not required for basal-level transcription, responsible for tissue- and time- specific gene expression Enhancers: always upstream of the gene within 100 bases of the transcription initiation site, TATA, CAAT, GC boxes, required for basal-level transcription T/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 the β -globin gene indicate that mutations in some areas are more likely than mutations in other areas to affect transcription rates. When mutations occur in consensus sequences (modular elements such as GC box, CAAT box, TATA box), does transcription increase or decrease? - decrease For the genotype, I + O+ Z+/ F' I + O+ Z+ which of the following should be entered into the chart?

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    Genotype I + 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 repressor I- = mutant repressor (unable to bind to the operator) Is = mutant repressor (insensitive to lactose) O+ = wild-type operator Oc = 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? Genotype I + 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 repressor I- = mutant repressor (unable to bind to the operator) Is = mutant repressor (insensitive to lactose) O+ = wild-type operator Oc = 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? Genotype I + O+ Z+/ F' I + O+ Z+ I - Oc Z-/ F' I- Oc Z-

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