2016考研英语阅读理解模拟题训练(3)
考研英语阅读部分分值比重大，占总分的40%，是毫无疑问的复习重点。英语阅读复习重在练习，通过练习掌握阅读技巧和做题方法，以争取再短时间内把握主旨和针对考题找出答案。新东方在线整理2016考研英语阅读理解模拟题训练集，同学们可以来测测自己的阅读水平哦！2016考研英语阅读理解模拟题训练(3)
Scientists have known for more than two decades that cancer is a disease of
the genes. Something scrambles the Dna inside a nucleus， and suddenly， instead
of dividing in a measured fashion， a cell begins to copy itself furiously.
Unlike an ordinary cell， it never stops. But describing the process isn't the
same as figuring it out. Cancer cells are so radically different from normal
ones that it's almost impossible to untangle the sequence of events that made
them that way. So for years researchers have been attacking the problem by
taking normal cells and trying to determine what changes will turn them
cancerous——always without success.
Until now. According to a report in the current issue of Nature， a team of
scientists based at M.I.T.'s Whitehead Institute for Biomedical Research has
finally managed to make human cells malignant——a feat they accomplished with two
different cell types by inserting just three altered genes into their DNA. While
these manipulations were done only in lab dishes and won't lead to any immediate
treatment， they appear to be a crucial step in understanding the disease. This
is a “landmark paper，” wrote Jonathan Weitzman and Moshe Yaniv of the Pasteur
Institute in Paris， in an accompanying commentary.
The dramatic new result traces back to a breakthrough in 1983， when the
Whitehead's Robert Weinberg and colleagues showed that mouse cells would become
cancerous when spiked with two altered genes. But when they tried such
alterations on human cells， they didn't work. Since then， scientists have
learned that mouse cells differ from human cells in an important respect： they
have higher levels of an enzyme called telomerase. That enzyme keeps caplike
structures called telomeres on the ends of chromosomes from getting shorter with
each round of cell division. Such shortening is part of a cell's aging process，
and since cancer cells keep dividing forever， the Whitehead group reasoned that
making human cells more mouselike might also make them cancerous.
The strategy worked. The scientists took connective-tissue and kidney cells
and introduced three mutated genes——one that makes cells divide rapidly; another
that disables two substances meant to rein in excessive division; and a third
that promotes the production of telomerase， which made the cells essentially
immortal. They'd created a tumor in a test tube. “Some people believed that
telomerase wasn't that important，” says the Whitehead's William Hahn， the
study's lead author. “This allows us to say with some certainty that it is.”
Understanding cancer cells in the lab isn't the same as understanding how
it behaves in a living body， of course. But by teasing out the key differences
between normal and malignant cells， doctors may someday be able to design tests
to pick up cancer in its earliest stages. The finding could also lead to drugs
tailored to attack specific types of cancer， thereby lessening our dependence on
tissue-destroying chemotherapy and radiation. Beyond that， the Whitehead
research suggests that this stubbornly complex disease may have a simple origin，
and the identification of that origin may turn out to be the most important step
of all.
注(1)：本文选自Time; 08/09/99， p60， 3/5p， 2c
注(2)：本文习题命题模仿对象2002年真题text 4
1. From the first paragraph， we learn that ________________.
scientists had understood what happened to normal cells that made them
behave strangely
when a cell begins to copy itself without stopping， it becomes
cancerous
normal cells do no copy themselves
the DNA inside a nucleus divides regularly
2. Which of the following statements is true according to the text?
The scientists traced the source of cancers by figuring out their DNA
order.
A treatment to cancers will be available within a year or two.
The finding paves way for tackling cancer.
The scientists successfully turned cancerous cells into healthy
cells.
3. According to the author， one of the problems in previous cancer research
is ________.
enzyme kept telomeres from getting shorter
scientists didn‘t know there existed different levels of telomerase
between mouse cells and human cells
scientists failed to understand the connection between a cell‘s aging
process and cell division.
human cells are mouselike
4. Which of the following best defines the word “tailored” (Line 4，
Paragraph 5)?
made specifically
used mainly
targeted
aimed
5. The Whitehead research will probably result in ___________.
a thorough understanding of the disease
beating out cancers
solving the cancer mystery
drugs that leave patients less painful
答案：B C B A D
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