Mastering Biology chapter 11

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The term “gene expression” refers to the
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process by which genetic information flows from genes to proteins.
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A gene operon consists of
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transcribed genes, an operator, and a promoter.
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In a prokaryote, a group of genes with related functions, along with their associated control sequences, defines
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an operon.
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The lac operon in Escherichia coli
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prevents lactose-utilizing enzymes from being expressed when lactose is absent from the environment.
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Proteins that bind to DNA and turn on operons by making it easier for RNA polymerase to bind to a promoter are called
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activators.
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The expression of the tryptophan operon is controlled by
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a repressor that is active when it binds to tryptophan.
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The lac operon of E. coli is ________ when the repressor is bound to lactose.
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active
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Which of the following is likely to occur in E. coli cells that are grown in skim milk?
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The trp repressor is activated, and the cells will produce lactose-utilizing enzymes.
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There is a mutation in the operator of the trp operon in a cell such that the trp repressor is unable to bind to the operator. If tryptophan is added to the cell, what will happen?
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Tryptophan will bind to the repressor, and trp enzymes will be produced.
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The basis of cellular differentiation is
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selective gene expression.
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The genes for the enzymes of glycolysis
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are active in all metabolizing cells, but the genes for specialized proteins are expressed only in particular cell types.
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The relationship between DNA and chromosomes is most like
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thread wrapped around a spool.
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In female mammals, the inactive X chromosome in each cell
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becomes a Barr body.
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Both prokaryotic and eukaryotic cells use ________ to turn certain genes on or off.
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proteins
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Enhancers are
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DNA sequences to which activator proteins bind.
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RNA splicing involves the
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removal of introns from the molecule.
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The coding regions of a gene are called
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exons.
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Which of the following permits a single gene to code for more than one polypeptide?
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alternative RNA splicing
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Small pieces of RNA that can regulate translation of mRNA are called
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microRNA
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RNA interference (RNAi) can be used by
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cells to prevent infections from double-stranded RNA viruses.
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All of the following mechanisms are used to regulate protein production except
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DNA replication.
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Which of the following mechanisms of controlling gene expression occurs outside of the nucleus?
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translation
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A homeotic gene
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serves as a master control gene that functions during embryonic development by controlling the developmental fate of groups of cells.
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Which of the following statements about microarrays is false?
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Microarrays use tiny portions of double-stranded RNA fragments from a large number of genes.
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In multicellular organisms, the coordination of cellular activities relies on
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cell-to-cell signaling and signal transduction pathways.
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To initiate a signal transduction pathway, a signal binds to a receptor protein usually located in the
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plasma membrane.
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Transcription factors attach to
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DNA
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A signal outside a cell triggers changes in the transcription and translation inside the cell through
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signal transduction pathways.
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Yeast are able to communicate with each other
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through chemical signaling.
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Signal transduction pathways
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are mechanisms of communication that probably evolved in ancient prokaryotes.
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In plants, most differentiated cells retain
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a complete set of their genes and retain the ability to express those genes under certain circumstances.
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Why can some plants be cloned from a single cell?
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Plant cells can dedifferentiate and give rise to all of the specialized cells required to produce an entire plant.
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Which of the following processes occurs when a salamander regenerates a lost limb?
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Certain cells in the limb dedifferentiate, divide, and then redifferentiate to form a new limb.
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The cloning of Dolly the sheep
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demonstrated that the nuclei from differentiated mammalian cells can retain their full genetic potential.
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The use of cloning to produce special embryonic stem cells is called
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therapeutic cloning.
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Which of the following mammals has not yet been cloned and brought through the complete gestation cycle?
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human
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Which of the following possible uses of reproductive cloning is still considered by most to be an unresolved ethical issue?
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the reproductive cloning of humans
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Adult stem cells have limited therapeutic potential
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because their developmental potential is limited to certain tissues.
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A gene that can cause cancer when present in a single copy in a cell is called a/an
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oncogene.
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Which of the following is not a factor that contributes to normal cells becoming cancerous?
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the production of more effective tumor-suppressor gene products
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Cancer of the colon is caused by
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several somatic cell gene mutations.
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The development of colon cancer occurs slowly, and colon cancer is more frequently seen in the elderly than the young. This is most likely because
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usually six or more somatic mutations must occur to give rise to the cancer, which takes time.
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Mutations in the proto-oncogene ras and the tumor suppressor gene p53
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disrupt normal regulation of the cell cycle.
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Mutations in the p53 gene can lead to cancer by
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causing the production of a faulty protein that is no longer able to inhibit cell division.
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The carcinogen known to cause the most cases and types of cancer is
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tobacco.
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Which of the following statements regarding cancer risk factors is false?
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Mutagens are usually not carcinogens.
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A cell has a mutation in both alleles of its p53 gene that causes the p53 protein to be three times as effective as normal. What do you predict would happen to this cell?
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The cell would divide normally or possibly not at all.
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In thinking about their role in cell division, oncogenes are like the ________ of a car, while tumor suppressor genes are like the ________ of a car.
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gas pedal; brakes
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Melanoma (skin cancer) can develop after several mutations occur in skin cells. If a woman is diagnosed with melanoma and becomes pregnant, what are the chances that her offspring will inherit melanoma?
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It is unlikely that the offspring will be born with melanoma.
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A cell is expressing the mutant form of ras, but one of the downstream relay proteins is not present because of another mutation. How will cell division be affected in this scenario?
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The cell will not divide at all unless other proteins that stimulate cell division are present.

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