掌握了gre阅读里的长难句，到了实战演习的时候了。gre阅读练习每日一篇帮助gre考生循序渐进地进行练习和总结。希望gre考生在进行gre阅读练习时，也按着考试时候的时间规定自己的练习，这样才能有效果。
It is well known that biological changes at the molecular level have morphogenetic consequences, consequences affecting the formation and differentiation of tissues and organs. It is superfluous to point out that gene mutations and disturbances of the bio-synthetic processes in the embryo may result in abnormalities in the morphology of an organism. However, whereas much is known about causes and consequences at the molecular level, and in spite of an enormous accumulation of chemical and morphological data on embryos of various kinds, our understanding of how genes control morphogenesis is still far from complete. Perhaps one reason for this is that molecular biologists and morphologists speak different languages. Whereas the former speak about messenger-RNA and conformational changes of protein molecules, the latter speak of ectoderms, hypoblasts, and neural crests.
One solution to this predicament is to try to find some phenomena relevant to morphogenesis which both the molecular biologist and the morphologist can understand and discuss. As morphogenesis must be basically the result of changes in behavior of the individual cells, it seems logical to ask morphologists to describe the morphogenetic events observed in terms of changes in cellular contact, changes in the rate of proliferation of cells, or similar phenomena. Once this is done, it may be appropriate to ask questions about the molecular background for these changes. One may, for instance, ask whether variations in cell contact reflect alterations in the populations of molecules at the cell surface, or one may inquire about the molecular basis for the increased cell mobility involved in cell dispersion.
Studies of this kind have been carried out with cells released from tissues in various ways and then allowed to reveal their behavior after being spread out into a thin layer. In many cases, such cells show the ability to reaggregate, after which different cell types may sort themselves out into different layers and even take part in still more intricate morphogenetic events. But in most cases, the behavior of cells in the intact embryo is difficult to study because of the thickness and opacity of the cell masses. The sea urchin embryo, however, has the advantage that it is so transparent that each cell can be easily observed throughout development. Thus, by recording the development of a sea urchin embryo with time-lapse photography, the research scientist might discover previously unknown features of cellular behavior. Perhaps the study of the sea urchin in this manner can provide a medium by which the molecular biologist and the morphologist can begin communicating with each other more effectively about the way in which genes control morphogenesis.
17. The authors primary purpose is to
outline a procedure and discuss possible applications
evaluate an experiment in terms of its applicability to medical research
propose a method for curing specific genetic disorders
explain a problem and suggest a solution for it
reveal the shortcomings of several attitudes toward genetic research
18. The author states that research into the genetic control of morphogenesis has been impeded by
an incomplete understanding of biomolecular reactions that are highly complex
a lack of communication between scientists whose work could be complementary
a reluctance on the part of morphologists to share data with molecular biologists
a lack of research in the area of morphology
the unavailability of suitable research equipment
19. The major objective of the authors proposal is to
devise a technique for proving that abnormalities in morphology result from gene mutations
improve the procedures for organizing chemical and morphological data
increase the accuracy of measurements of cell populations and cell mobility
reduce the margin of error in the study of conformational changes of protein molecules
provide a plan for increasing knowledge about the influence of genes on morphogenesis
20. It can be inferred from the passage that some cells that have been isolated from an organism have the ability to
control morphogenesis
reform to make higher organisms
reorganize to form clusters of cells
regulate the transmission of light through the cell wall
regulate the rate of tissue formation
21. It can be inferred from the passage that the study of the effects of genes on morphogenesis is best accomplished by observing
intact developing embryos
adult sea urchins
isolated living cells
groups of genetically mutated cells
cells from the same kink of tissue
22. According to the passage, it is difficult to study cells in most intact embryos because
morphogenetic events cannot be isolated
embryos die quickly
embryos are difficult to obtain
individual cells reaggregate too quickly
individual cells are difficult to see
23. Which of the following sequences best describes the authors suggestion for future research on morphogenesis?
Accumulation of data, simplification of language, explanation of morphogenesis
Dispersion of cells, evaluation of cell activity, development of an explanatory hypothesis
Classification of cell types, separation of cell, observation of cell activity
Observation of cell development, description of cell behavior, explanation at the molecular level
Differentiation of cell types, description of cell structure, analysis of molecular components
24. The tone of the authors discussion of the difference in the language used by morphologists and that used by molecular biologists is one of
indifference
neutrality
derision
approbation
indignation
The black experience, one might automatically assume, is known to every Black author. Henry James was pondering a similar assumption when he said: You were to suffer your fate. That was not necessarily to know it. This disparity between an experience and knowledge of that experience is the longest bridge an artist must cross. Don L. Lee, in his picture of the Black poet, studying his own poetry and the poetry of other Black poets, touches on the crucial point. In order to transform his own sufferingsor joysas a Black person into usable knowledge for his readers, the author must first order his experiences in his mind. Only then can he create feelingly and coherently the combination of fact and meaning that Black audiences require for the reexploration of their lives. A cultural community of Black authors studying one anothers best works systematically would represent a dynamic interchange of the spiritcorrective and instructive and increasingly beautiful in its recorded expression.
25. It can be inferred from the passage that the author considers poetry to be which of the following?
A means of diversion in which suffering is transformed into joy
An art form that sometimes stifles creative energy
A bridge between the mundane and the unreal
A medium for conveying important information
An area where beauty must be sacrificed for accuracy
26. It can be inferred from the passage that the author would be LEAST likely to approve of which of the following?
Courses that promote cultural awareness through the study of contemporary art
The development of creative writing courses that encourage mutual criticism of student work
Growing interest in extemporaneous writing that records experiences as they occur
A shift in interest from abstract philosophical poetry to concrete autobiographical poetry
Workshops and newsletters designed to promote dialogues between poets
27. The author refers to Henry James primarily in order to
support his own perception of the longest bridge
illustrate a coherent combination of fact and meaning
provide an example of dynamic interchange of the spirit
establish the pervasiveness of lack of self-knowledge
contrast Jamess ideas about poetry with those of Don L. Lee
答案：17-27：DBECAEDBDCA
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