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2011-09-14 15:05:00   来源：作文地带    双击单词自动翻译

　　(D) Degradation of mRNA is now considered to be the key process and mRNA synthesis is no longer believed to play a significant role.

　　(E) Degradation of mRNA is now considered to be as important as mRNA synthesis has been, and still is, believed to be.

　　7. According to the passage, which of the following can happen when protein synthesis is not appropriately regulated?

　　(A) Diabetes can result from errors that occur when the ribosomes translate mRNA into protein.

　　(B) Cancer can result from an excess of certain proteins and diabetes can result from an insulin deficiency.

　　(C) A deficiency of red blood cells can occur if bone marrow cells produce too much hemoglobin.

　　(D) Cancer can be caused by excessively rapid degradation of certain amino acids in the cytoplasm of cells.

　　(E) Excessive synthesis of one protein can trigger increased degradation of mRNA’s for other proteins and create severe protein imbalances.

　　8. The passage suggests that a biologist who detected high levels of two proteins in a certain type of cell would be likely to consider which of the following as a possible explanation?

　　(A) The rate of mRNA degradation for one of the proteins increases as this type of cell develops a more specialized function.

　　(B) The two proteins are most likely constituents of a complex substance supporting the cells’ specialized function.

　　(C) The cells are likely to proliferate abnormally and possibly become cancerous due to the levels of these proteins.

　　(D) The mRNA’s for both proteins are being degraded at a low rate in that type of cell.

　　(E) The mRNA’s for the two proteins are being synthesized at identical rates in that type of cell.

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