mastering bio- chapter 18 – Flashcards
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The trp repressor blocks transcription of the trp operon when the repressor _____.
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binds to tryptophan
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_____ bind(s) to DNA enhancer regions.
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Activators
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Which of these indicates an enhancer region?
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A. (the beginning of the cycle)
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Which of these directly bind(s) to the promoter?
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C and D
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DNA methylation is a mechanism used by eukaryotes to do what?
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inactivate genes
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Imagine that you've isolated a yeast mutant that contains histones resistant to acetylation. What phenotype do you predict for this mutant?
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The mutant will show low levels of gene expression.
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Not long ago, it was believed that a count of the number of protein-coding genes would provide a count of the number of proteins produced in any given eukaryotic species. This is incorrect, largely due to the discovery of widespread _____.
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alternative splicing
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Which of the following is most likely to have a small protein called ubiquitin attached to it?
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a cyclin protein, that usually acts in G1, in a cell that is in G2
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Which of these is true of the cytoplasm of an unfertilized egg?
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It is an unevenly distributed mixture of mRNA, proteins, organelles, and other substances.
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How do cells become differentiated?
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Different genes are expressed so that different proteins are produced.
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The bicoid gene product is normally localized to the anterior end of the embryo. If large amounts of the product were injected into the posterior end as well, which of the following would occur?
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Anterior structures would form in both ends of the embryo.
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Which of the following would be most likely to lead to cancer?
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amplification of a proto-oncogene and inactivation of a tumor-suppressor gene
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The product of the p53 gene _____.
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inhibits the cell cycle
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Forms of the Ras protein found in tumors usually cause which of the following?
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excessive cell division
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How are genes coordinately controlled in eukaryotic cells?
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1. Coordinately controlled genes in eukaryotic cells share a set of control elements.
2. Coordinately controlled genes in eukaryotic cells are activated by the same chemical signals.
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It is possible for a cell to make proteins that last for months; hemoglobin in red blood cells is a good example. However, many proteins are not this long-lasting; they may be degraded in days, hours, or even minutes. What is the advantage of short-lived proteins?
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Short-lived proteins enable the cells to control their activities precisely and efficiently.
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Which of the following mechanisms is (are) used to coordinate the expression of multiple, related genes in eukaryotic cells?
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The genes share a single common enhancer, which allows appropriate activators to turn on their transcription at the same time
