编辑点评: GRE阅读考试的材料,非常强调逻辑的关系,所以逻辑要点是大家在解GRE阅读题的时候的关键,本文就为大家例举了这样一篇逻辑短文,供大家参考和练习。
随着GRE阅读考试的难度日益增加,大家需要有针对性地进行练习,本文为大家例举的就是逻辑短文的练习,文末还附有答案,供大家更好地练习。
Until about five years ago, the very idea that peptide hormones might be made anywhere in the brain besides the hypothalamus was astounding. But laboratory after laboratory found that antiserums to peptide hormones, 5 when injected into the brain, bind in places other than the hypothalamus, indicating that either the hormones or substances that cross-react with the antiserums are present.The immunological method of detecting peptide hormones by means of antiserums, however, is 10 imprecise. Cross-reactions are possible and this method cannot determine whether the substances detected by the antiserums really are the hormones, or merely close relatives.
Furthermore, this method cannot be used to determine the location in the body where the detected 15 substances are actually produced. New techniques of molecular biology, however, provide a way to answer these questions. It is possible to make specific complementary DNA s that can serve as molecular probes to seek out the messenger RNA s 20 of the peptide hormones. The brain cells containing these mRNA s can then be isolated and their mRNA s decoded to determine just what their protein products are and how closely the products resemble the true peptide hormones.
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