8
,8-1 A neuron and a white blood cell have very different functions. For example, a
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neuron can receive and respond to electrical signals while a white blood cell
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defends the body against infection. This is because ______.
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(a) the proteins found in a neuron are completely different from the proteins
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found in a white blood cell.
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(b) the neuron and the white blood cell within an individual have the same
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genome.
(c) the neuron expresses some mRNAs that the white blood cell does not.
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(d) neurons and white blood cells are differentiated cells and thus no longer
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need to transcribe and translate genes.
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(c)the neuron expresses some mRNAs that the white blood cell does not.kr kr kr kr kr kr kr kr kr kr kr
8-2 The distinct characteristics of different cell types in a multicellular organism
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result mainly from the differential regulation of the _________________.
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(a) replication of specific genes.
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(b) transcription of genes transcribed by RNA polymerase II.
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(c) transcription of housekeeping genes.
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(d) proteins that directly bind the TATA box of eukaryotic genes.
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(b)transcription of genes transcribed by RNA polymerase II. kr kr kr kr kr kr kr
8-3 The human genome encodes about 21,000 protein-coding genes.
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Approximately how many such genes does the typical differentiated human kr kr kr kr kr kr kr kr kr
cell express at any one time?
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(a) 21,000—all of them
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(b) between 18,900 and 21,000—at least 90% of the genes
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(c) between 5000 and 15,000
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(d) less than 2100
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8-4 Which of the following is not a good example of a housekeeping protein?
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(a) DNA repair enzymes
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, (b) histones
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(c) ATP synthase
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(d) hemoglobin
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8-5 Which of the following statements about differentiated cells is true?
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(a) Cells of distinct types express nonoverlapping sets of transcription factors.
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(b) Once a cell has differentiated, it can no longer change its gene expression.
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(c) Once a cell has differentiated, it will no longer need to transcribe RNA.
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(d) Some of the proteins found in differentiated cells are found in all cells of a
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multicellular organism. kr
(d)Some of the proteins found in differentiated cells are found in all cells of a kr kr kr kr kr kr kr kr kr kr kr kr kr kr
multicellular organism kr
8-6 Investigators performed nuclear transplant experiments to determine
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whether DNA is altered irreversibly during development. Which of the
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following statements about these experiments is true?
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(a) Because the donor nucleus is taken from an adult animal, the
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chromosomes from the nucleus must undergo recombination with the kr kr kr kr kr kr kr kr
DNA in the egg for successful development to occur.
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(b) The embryo that develops from the nuclear transplant experiment is
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genetically identical to the donor of the nucleus. kr kr kr kr kr kr kr
(c) The meiotic spindle of the egg must interact with the chromosomes of the
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injected nuclei for successful nuclear transplantation to occur.
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(d) Although nuclear transplantation has been successful in producing
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embryos in some mammals with the use of foster mothers, evidence of
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DNA alterations during differentiation has not been obtained for plants.
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(b)The embryo that develops from the nuclear transplant experiment is kr kr kr kr kr kr kr kr kr
genetically identical to the donor of the nucleus kr kr kr kr kr kr kr
8-8 Which of these method(s) of controlling eukaryotic gene expression is NOT
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