25个考研英语阅读经典试题及答案(13)医学类

2021年1月26日发(作者：acquire的用法)

25
个考研英语阅读经典试题及答案
(13)

SAMPLE 13
[
医学类
]
题目序号题型归类

第
1
题中心主旨题型

第
2
题审题定位题型

第
3
题细节推导题型

第
4
题句间关系题型

第
5
题细节推导题型

Until about five years ago, the very idea that peptide hormones might be made anywhere in
the
brain
besides
the
hypothalamus
was
astounding.
Peptide
hormones,
scientists
thought,
were
made
by
endocrine
glands
and
the
hypothalamus
was
thought
to
be
the
brains’
only
endocrine
gland. What is more, because peptide hormones cannot cross the blood-brain barrier, researchers
believed that they never got to any part of the brain other than the hypothalamus, where they were
simply produced and then released into the bloodstream.
But
these
beliefs
about
peptide
hormones
were
questioned
as
laboratory
after
laboratory
found that antiserums to peptide hormones, when injected into the brain, bind in places other than
the
hypothalamus,
indicating
that
either
the
hormones
or
substances
that
cross-react
with
the
antiserums
are
present.
The
immunological
method
of
detecting
peptide hormones by
means
of
antiserums, however, is imprecise. Cross-reactions are possible and this method cannot determine
whether
the
substances
detected
by
the
antiserums
really
are
the
hormones,
or
merely
close
relatives. Furthermore, this method cannot be used to determine the location in the body where the
detected substances are actually produced.
New techniques of molecular biology, however, provide a way to answer these questions. It
is possible to make specific complementary DNA’s (c DNA’s) that can serve as molecular probes

seek out the messenger RNA’s

(mRNA’s) of the peptide hormones. If brain cells are making the
hormones, the cells will contain these mRNA’s. If the products the brain cells make resemble the
hormones but are not identical to them, then the c DNA’s should still bind to these mRNA’s, bu
t
should not bind as tightly as they would to m RNA’s for the true hormones. The cells containing
these
mRNA’s
can
then
be
isolated
and
their
mRNA’s
decoded
to
determine
just
what
their
protein products are and how closely the products resemble the true peptide hormones.
The molecular approach to detecting peptide hormones using cDNA probes should also be
much faster than the immunological method because it can take years of tedious purifications to
isolate peptide hormones and then develop antiserums to them. Roberts, expressing the sentiment
of many researchers, states: “I was trained as an endocrinologist. But it became clear to me that
the
field
of
endocrinology
needed
molecular
biology
input.
The process
of grinding
out
protein
purifications is just too
slow.”

If, as the initial tests with cDNA probes suggest, peptide hormones really are made in brain
in areas other than the hypothalamus, a theory must be developed that explains their function in
the brain. Some have suggested that the hormones are all g
rowth regulators, but Rosen’s work on
rat brains indicates that this cannot be true. A number of other researchers propose that they might
be used for intercellular communication in the brain.
1. Which of the following titles best summarizes the text?
[A]
Is
Molecular
Biology
the
Key
to
Understanding
Intercellular
Communication
in
the
Brain?
[B]
Molecular
Biology:
Can
Researchers
Exploit
Its
Techniques
to
Synthesize
Peptide
Hormones?
[C]
The
Advantages
and
Disadvantages
of
the
Immunological
Approach
to
Detecting
Peptide Hormones.
[D]
Peptide
Hormones:
How
Scientists
Are
Attempting
to
Solve
Problems
of
Their
Detection and to Understand Their Function?
2. The text suggests that a substance detected in the brain by use of antiserums to peptide
hormones may

[A] have been stored in the brain for a long period of time.
[B] play no role in the functioning of the brain.
[C] have been produced in some part of the body other than the brain.
[D] have escaped detection by molecular methods.
3. According to the text, confirmation of the belief that peptide hormones are created in the
brain in areas other than the hypothalamus would force scientists to
[A] reject the theory that peptide hormones are made by endocrine glands.
[B] revise their beliefs about the ability of antiserums to detect peptide hormones.
[C]
invent
techniques
that
would
allow
them
to
locate
accurately
brain
cells
that
produce
peptide hormones.
[D] develop a theory that account for the role played by peptide hormones in the brain.
4.
Which
of
the
following
is
mentioned
in
the
text
as
a
drawback
of
the
immunological
method of detecting peptide hormones?
[A] It cannot be used to detect the presence of growth regulators in the brain.
[B] It cannot distinguish between the peptide hormones and substances that are very similar
to them.
[C] It uses antiserums that are unable to cross the blood- brain barrier.
[D] It involves a purification process that requires extensive training in endocrinology.
5. The idea that the field of endocrinology can gain from developments in molecular biology
is regarded by Roberts with
[A] incredulity.
[B] derision.