Biology Chapter 19 – Flashcards
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In humans and other mammals, dosage compensation is achieved by:
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females randomly inactivating one X chromosome in each cell.
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Gene regulation can occur at which of the following steps in the path from DNA to protein?
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during transcription from a chromosome, during translation from DNA to RNA and after protein synthesis
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Regulatory transcription factors: (select all correct choices)
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bind to DNA sequences in or near enhancer genes.
recruit components of the transcriptional complex of proteins.
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Epigentic mechanisms of gene regulation ___________ and are ___________.
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can be inherited by daughter cells; often reversible and responsive to environmental change
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In prokaryotes, inducers are small molecules that:
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bind to repressors and promote transcription.
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Which of the following questions is about gene regulation? Select all correct choices.
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Where are genes for hemoglobin expressed?
How much insulin is produced after a meal?
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Histone modification
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can change over time in response to environmental cues, allowing genes to be turned on or off as needed.
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Gene regulation by siRNA is ____________ in eukaryotes and may have evolved originally as a ____________.
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widespread; defense against viruses
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In RNA editing:
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enzymes change the base sequence of the primary transcript and therefore the protein for which it codes.
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An operon is:
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a region of DNA consisting of the promoter, operator, and coding sequence for structural proteins.
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The process by which a single primary RNA transcript is used to make multiple proteins is called:
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alternative splicing.
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Which of the following changes could cause the production of a shorter-than-normal protein from a gene? (Select all that apply.)
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changes in RNA processing
changes in RNA editing
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For the lactose operon, lactose is a(n):
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inducer
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For the lactose operon, the CRP-cAMP is a(n):
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activator
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At the molecular level, the "choice" between lytic and lysogenic pathways is determined by:
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the positive and negative regulatory effects of a small number of bacteriophage proteins produced soon after infection.
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Chromatin remodeling refers to the process by which:
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nucleosomes are repositioned to expose different stretches of DNA to the nuclear environment.
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The 5' UTR and 3' UTR of mRNA: (select all correct choices)
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-may bind with proteins that transport the mRNA to a specific region in the cell for translation.
-may bind with proteins that are localized to one place in the cell and that prevent translation.
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The CRP-cAMP complex binds the lactose operon when:
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glucose levels are low and cAMP levels are high.
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Both miRNA and siRNA work in conjunction with:
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a protein complex called RISC to bind primary RNA transcripts in the cytoplasm.
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A CpG island is: (select all correct choices)
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a cluster of alternating C and G bases in a small region near or in the promoter site of a gene
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RNA splicing provides an opportunity for regulating gene expression because
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a spliceosome in one cell can "see" as an intron what another spliceosome in another cell "sees" as an exon, allowing different proteins to be produced from the same primary transcript.
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Positive and negative transcriptional regulation differ in that:
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in positive regulation, the binding of a regulatory protein to the DNA is necessary for transcription to occur; in negative regulation, such binding prevents transcription.
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The structural genes of the lactose operon are: (select all correct choices)
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-turned off by the presence of lactose.
-always expressed unless the operon is turned off by a repressor.
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De-methylation of CpG islands can cause activation of transcription of nearby genes. Which modification to histone tails is most likely to result from this type of CpG de-methylation? (Select all that apply.)
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triple methylation of lysine on the histone tails
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Combinatorial control refers to the fact that:
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each gene has a unique combination of several different enhancers.
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In prokaryotes, gene expression is regulated at the level of: (select all correct choices)
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-transcription.
-translation.
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Small interfering RNA (siRNA) regulates gene expression by:
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inhibiting translation by degrading RNA transcripts
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The major mechanism of translational regulation is:
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the availability of initiation complex proteins in the cytoplasm.
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Activator proteins in prokaryotes experience shape changes in the presence or absence of small molecules. As a consequence: (select all correct choices)
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-they may activate genes needed only when such a small molecule is present in the cell.
-they may activate genes necessary to synthesize a specific small molecule.
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The lacZ and lacY genes are transcribed when:
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lactose is present and glucose levels are low.
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X chromosome inactivation is caused by the accumulation of
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non-coding RNA produced by the Xist gene, which coats the X chromosome and induces methylation, histone modification, and other changes associated with preventing transcription.
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A typical gene has ____________ enhancer sequence(s); each enhancer sequence has ____________ regulatory transcription factor(s).
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several; one
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In general, when cytosine bases in CpG islands are methylated:
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transcription is repressed.
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Dosage compensation refers to the fact that:
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X chromosome genes must be regulated differently in males and females because members of one sex have 2 X chromosomes, whereas members of the other have only 1.
