大学生物专业英语lesson_four.ppt

* * SciFinder??is a research discovery tool, suitable for both professional searchers and research scientists. You do not have to be an expert searcher to use SciFinder. Many organizations around the world use SciFinder to give their scientists direct access to CAS databases. SciFinder offers a one-stop shop experience with flexible search and discover options based on user input and workflow. You can search for substances, reactions, and patent and journal references anytime, anywhere. * * * * * * * * * * * * 是被引用次数最多的综合学科文献之一，周刊。它是美国科学院的院刊，亦是公认的世界四大名刊之一。 美国《国家科学院院刊》（PNAS）由美国国家科学院创建于1914年，每周出版一次，是目前世界上引用率最高的科学期刊之一。Proceedings of the National Academy of Sciences * * * * * * * * * * * * * * His revolutionary ideas were neither understood nor accepted until many years after Mendel died. 直到他去世后若干年，他的创新性的理论才被理解和接受。 * * 3. Mendel’s Classic Experiments孟德尔的经典实验 * * Mendel studied genetics through plant-breeding experiments with the garden pea, a plant that is self-fertilizing and breeds [bri:d] true (each offspring is identical to the parent in the trait of interest). 孟德尔通过豌豆育种实验来研究遗传学，豌豆是自花授粉的,并且是真实遗传的(每个子代和亲本的遗传特征是一样的)。 * * To test the blending theory, he focused his research on seven distinct characters. 为验证混合理论，他的研究主要集中在7个不同的特征上。 * * Each of these characters, such as seed color and plant height, present only two, clear-cut possibilities. 每个特征如种子颜色，植株高度等，都只有两个明确的可能性。 He also recorded the type and number of all progeny produced from each pair of parent pea plants, and followed the results of each cross for two generations. 他也记录了来自于每一对亲本的所有子代的类型和数量，和两个子代杂交的结果。 * * For each of the characters he studied, Mendel found that one trait was dominant [d?min?nt] while the other was recessive [risesiv] . 对于他研究的每个特征而言，孟德尔发现一个特征是显性的,那么另一个就是隐性的。 In the second filial [filj?l] (F2) generation, the ratio of dominant to recessive was 3:1. 在子2代中, 显性与隐性比为3∶1。 * * Mendel deduced that this results was possible only if each individual possesses only two hereditary units, one fr