专八改错练习1 ? One important outcome of the work on the expression of genes in developing embryos is sure to be knowledge that can help preventing birth defects. Just as promising (26) is the possibility of unraveling the complicated writing (27) of the brain. A mechanic gets valuable insight how an (28) automobile works by rebuilding car engines; similarly, neuroscientists can learn how the brain functions from (29) the way it is put together. The next step pursuing the (30) goal is to find out how the blueprint genes, the home box genes, control the expression of other genes that create the valves and piston of the working cerebral engine. The protein encoded by the latter genes could change the (31) stickiness of the cell surface, the shape of the cell or its metabolism ?to create the characteristic peculiar to, say, neurons or neural-crest cell. Surface proteins may be the (32) mechanism, whereby similar programmed cells stick together to form specific structures; they might also sense (33)the local environment to help the cell decide what is to do. Clarifying those mechanisms will engage the best talents in (34) embryology and molecular biology for some times to come. (35) What is perhaps the most intriguing question of all is if the brain is powerful enough to solve the puzzle of its own creation. 26.preventing改为prevent 27.complicated改为complexion? 28.sight后加into 29.neuroscientist改为a neuroscientist 30.pursuing后加in 31.later改为latter 32.similar改为similarly 33.去掉is 34.times改为time 35.if改为whether 专八改错练习2 Vitamins, like minerals, are chemicals. There is absolutely not difference in the chemical structure (26) of the nature vitamin C and the chemical structure (27) of the synthetic vitamin C. Also, while most sub- stances are harmless at very low level of intake, all (28) substance -- even the elements that are essential to life -- can be dangerous if you overdo them. Take water for example. Six or eight glasses a day will keep your body in good fluid balance. But you can also be drown (29) in it. Some people argue that individuals vary greatly (30) in their need for nutrients, it cannot necessarily be stated any given amount is too much; that is all (31) relative. But since there is little solid information on what is the optimal intake of any essential nutrient in healthy individuals, it would be impossible to give guidelines that take these proportional needs into the (32) account. Just as with other drugs, the relation to (33) different vitamin dosages varies, with some people better able than others to tolerate large amounts. While we do know that very specifically what the toxic level (34) is for vitamins A and D, we are far less sure about vitamin E, even though it, too, is fat-soluble, and we still don’t understand the water-soluble vitamin, the C (35) and the B groups, which the body cant store. 26.not改为no 27.nature改为natural 28.at后加a 29.去掉be 30.that后加? 31.stated后加that? 32. 去掉the 33. relation改为reaction? 34.去掉that 35. vitamin改为vitamins
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