Mastering Biology Chapter 18 – Flashcards

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___________ is the process by which information encoded in DNA is converted to information encoded in RNA.
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Transcription
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In humans, the hormone testosterone enters cells and binds to specific proteins, which in turn bind to specific sites on the cells' DNA. These proteins probably act to do what?
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help RNA polymerase transcribe certain genes
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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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The phenomenon in which RNA molecules in a cell are destroyed if they have a sequence complementary to an introduced double-stranded RNA is called _____.
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RNA interference
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Which of the following best describes siRNA? A) a double-stranded RNA that is formed by cleavage of hairpin loops in a larger precursor B) a double-stranded RNA, one of whose strands can complement and inactivate a sequence of mRNA C) a single-stranded RNA that can, where it has internal complementary base pairs, fold into cloverleaf patterns D) a portion of rRNA that allows it to bind to several ribosomal proteins in forming large or small subunits
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B) a double-stranded RNA, one of whose strands can complement and inactivate a sequence of mRNA
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How do master regulatory genes function in cell differentiation?
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1. The transcription factors they produce coordinately control related genes. 2. They are often capable of changing some fully differentiated cells of different types into their particular cell type. 3. They may produce proteins that stimulate production of more of the master regulatory gene. 4. They produce proteins that act as transcription factors to produce proteins specific to the function of the particular cell type.
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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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A cell is considered to be differentiated when it _____.
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produces proteins specific to a particular cell type
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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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The primary difference between enhancers and promoter-proximal elements is that enhancers _____.
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are at considerable distances from the promoter; promoter-proximal elements are close to the promoter
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The reason for differences in the sets of proteins expressed in a nerve and a pancreatic cell of the same individual is that nerve and pancreatic cells contain different _____.
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sets of regulatory proteins
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Gene expression is often assayed by measuring the level of mRNA produced from a gene. If one is interested in knowing the amount of a final active gene product, a potential problem of this method is that it ignores the possibility of _____.
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translational control
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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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One way to detect alternative splicing of transcripts from a given gene is to _____.
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compare the sequences of different mRNAs made from the given gene
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In one set of experiments she succeeded in increasing acetlylation of histone tails. Which of the following results would she most likely see?
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decreased chromatin condensation
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miRNAs can control gene expression by what action?
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binding to mRNAs and degrading them or blocking their translation
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Some time later, she finds that the introduced strand separates into single-stranded RNAs, one of which is degraded. What does this enable the remaining strand to do?
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bind to complementary regions of target mRNAs
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The fact that plants can be cloned from somatic cells demonstrates that _____.
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differentiated cells retain all the genes of the zygote
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In colorectal cancer, several genes must be mutated for a cell to develop into a cancer cell. Which of the following kinds of genes would you expect to be mutated?
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genes involved in control of the cell cycle
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Which of the following would be most likely to lead to cancer? A) amplification of a proto-oncogene and inactivation of a tumor-suppressor gene B) hyperactivity of a proto-oncogene and activation of a tumor-suppressor gene C) hyperactivity of both a proto-oncogene and a tumor-suppressor gene D) failure of a proto-oncogene to produce a protein and amplification of a tumor-suppressor gene E) failure of both a proto-oncogene and a tumor-suppressor gene to produce proteins
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A) amplification of a proto-oncogene and inactivation of a tumor-suppressor gene
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All your cells contain proto-oncogenes, which can change into cancer-causing genes. Why do cells possess such potential time bombs?
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Proto-oncogenes are necessary for the normal control of cell growth and division
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Which of the following types of mutation would convert a proto-oncogene into an oncogene?
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a mutation that greatly increases the amount of the proto-oncogene protein
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Proto-oncogenes _____.
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stimulate normal cell growth and division
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The product of the p53 gene _____.
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inhibits the cell cycle
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Tumor-suppressor genes _____.
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encode proteins that help prevent uncontrolled cell growth
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BRCA1 and BRCA2 are considered to be tumor-suppressor genes because _____.
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their normal products participate in repair of DNA damage
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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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Muscle cells differ from nerve cells mainly because they
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express different genes.
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Cell differentiation always involves
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the production of tissue-specific proteins, such as muscle actin.
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Which of the following is an example of post-transcriptional control of gene expression? A)gene amplification contributing to cancer B)the removal of introns and alternative splicing of eons C)the binding of transcription factors to a promoter D)the folding of DNA to form heterochromatin E)the addition of methyl groups to cytosine bases of DNA
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B)the removal of introns and alternative splicing of exons
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Within a cell, the amount of protein made using a given mRNA molecule depends partly on
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the rate at which the mRNA is degraded.
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