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大家好，5.1.总结了十几篇og文章，算来应该是第三遍了，突然对gmat感觉好多了，边阅读，边试着预测考点，能猜对50%-60%（也许是回忆的关系，我也不知道）。
尽管还有错误，但知道碰到类似的题目怎样可以少错一点，或者说gmat的常用陷阱，比如文学类的文章主题是compare, or contrast passage, or article, or so on 千万不要将讨论的内容作为主体。
现在将我最薄弱的生物类文章的分析，共享出来。目的1是作为自己的节日总结 2是为了献丑，请各位牛牛指正。小安，不知我是不是理解了你的方法？（it is your former trainee xixi)
Passage 24
All of the cells in a particular plant start out with the
same complement of genes. How then can these cells
differentiate and form structures as different as roots,
stems, leaves, and fruits? The answer is that only a
(5) small subset of the genes in a particular kind of cell are
expressed, or turned on, at a given time. This is accom-
plished by a complex system of chemical messengers
that in plants include hormones and other regulatory
molecules. Five major hormones have been identified:
(10) auxin, abscisic acid, cytokinin, ethylene, and gibberel-
lin. Studies of plants have now identified a new class of
regulatory molecules called oligosaccharins.
Unlike the oligosaccharins, the five well-known plant（Q69,Q72）
hormones are pleiotropic rather than specific, that is,
(15) each has more than one effect on the growth and devel-
opment of plants. The five has so many simultaneous(Q67,Q71)
effects that they are not very useful in artificially
controlling the growth of crops. Auxin, for instance,(Q70)
stimulates the rate of cell elongation, causes shoots to
(20) grow up and roots to grow down, and inhibits the
growth of lateral shoots. Auxin also causes the plant to
develop a vascular system, to form lateral roots, and to
produce ethylene.
The pleiotropy of the five well-studied plant
(25) hormones is somewhat analogous to that of certain(Q68)
hormones in animal. For example, hormones from the
hypothalamus in the brain stimulate the anterior lobe
of the pituitary gland to synthesize and release many
different hormones, one of which stimulates the release
(30) of hormones from the adrenal cortex. These hormones
have specific effects on target organs all over the body.
One hormone stimulates the thyroid gland, for
example, another the ovarian follicle cells, and so forth.
In other words, there is a hierarchy of hormones.
(35) Such a hierarchy may also exist in plants. Oligosac-
charins are fragments of the cell wall released by
enzymes: different enzymes release different oligosac-
charins. There are indications that pleiotropic plant
hormones may actually function by activating the (Q69,Q71)
(40) enzymes that release these other, more specific chemical
messengers from the cell wall.
67. According to the passage, the five well-known plant hormones are not useful in controlling the growth of crops because
(A) it is not known exactly what functions the hormones perform（无关）
(B) each hormone has various effects on plants(L16原文替换)
(C) none of the hormones can function without the others（无关）
(D) each hormone has different effects on different kinds of plants（无关）
(E) each hormone works on only a small subset of a cell’s genes at any particular time（无关）
68. The passage suggests that the place of hypothalamic hormones in the hormonal hierarchies of animals is similar to the
place of which of the following in plants?
(A) Plant cell walls（无关）
(B) The complement of genes in each plant cell（无关）
(C) A subset of a plant cell’s gene complement（无关）
(D) The five major hormones（L24原文替换，similar to…对应 analogous to）
(E) The oligosaccharins（无关）
69. The passage suggests that which of the following is a function likely to be performed by an oligosaccharin?
(A) To stimulate a particular plant cell to become part of a plant’s root system(L13的改写，be specific 对应 a particular plant cell)
(B) To stimulate the walls of a particular cell to produce other oligosaccharins（无关）
(C) To activate enzymes that release specific chemical messengers from plant cell walls（与原文相反，主动与被动相反以上当）
(D) To duplicate the gene complement in a particular plant cell（无关）
(E) To produce multiple effects on a particular subsystem of plant cells（与原文相反，即两个比较的相反，unlike….）
70. The author mentions specific effects that auxin has on plant development in order to illustrate the
(A) point that some of the effects of plant hormones can be harmful(偷换概念, not useful≠ harmful,易错)
(B) way in which hormones are produced by plants（主被动语态相反，实际是hormones’ effect on plants）
(C) hierarchical nature of the functioning of plant hormones（无关）
(D) differences among the best-known plant hormones（不精确，一个例子不能说明differences）
(E) concept of pleiotropy as it is exhibited by plant hormones(pleiotropy≌ various,二段的中心句)
71. According to the passage, which of the following best describes a function performed by oligosaccharins?
(A) Regulating the daily functioning of a plant’s cells
(B) Interacting with one another to produce different chemicals
(C) Releasing specific chemical messengers from a plant’s cell walls
(D) Producing the hormones that cause plant cells to differentiate to perform different functions
(E) Influencing the development of a plant’s cells by controlling the expression of the cells’ genes (information题，必须关联前后进行推论，才可获得)
72. The passage suggests that, unlike the pleiotropic hormones, oligosaccharins could be used effectively to
(A) trace the passage of chemicals through the walls of cells（无关）
(B) pinpoint functions of other plant hormones（无关）
(C) artificially control specific aspects of the development of crops(原文改写，与Q69为同一个考点)
(D) alter the complement of genes in the cells of plants（无关）
(E) alter the effects of the five major hormones on plant development（无关）
总结：
1. 考的引导词：（详见匡起来的字）
l unlike(强对比)，
l for instance, for example(举例)
l  引号补充说明前面的内容)
2. 考点分析：
l Q67,69,72 考的是同一件事情：unlike a,b…只是问法不同，67：mormone, 69 ligo, 72ligo unlike的一段话，通过对比说明five hormones的effect, 丛考的次数及方法足以看出在生物类文章中，对比的重要性
l Q68：三段的主体句，并通过例子来说明
l Q70:二段的主体句，并通过例子来说明
l Q71：information 题：较难需推出
3. 个人感觉：
l 考点非常清晰，特别是考对比
l 不仅考对five hormone and olig 相互关系，还考对于选项的判别能力，以主被动，相反选项混淆）
l 由于文章不仅说一件事，没有考到topic
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发表于 2004-5-7 01:00:00
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