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TheAnuja55
- Senior | Next Rank: 100 Posts
- Posts: 35
- Joined: Wed Jul 27, 2011 12:35 am
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Still am too bad at RCs. I'm following the strategy given in the GMATPrepnow of neatly paraphrasing and getting gist of the passage but even now am worst in RCs. I'am getting only 3-4 correct out of 6, and the following passage was the ultimate nightmare !! Just 2 correct answers out of 6. And for my GMAT only 10 days to go. Is there any other strategy or suggestion please?
All 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 small subset of the genes in a
particular kind of cell are expressed, or turned on,
at a given time. This is accomplished by a complex
system of chemical messengers that in plants
include hormones and other regulatory molecules.
Five major hormones have been identified: auxin,
abscisic acid, cytokinin, ethylene, and gibberellin.
Studies of plants have now identified a new class of
regulatory molecules called oligosaccharins.
Unlike the oligosaccharins, the five well-known
plant hormones are pleiotropic rather than specific;
that is, each has more than one effect on the
growth and development of plants. The five have
so many simultaneous effects that they are not
very useful in artificially controlling the growth of
crops. Auxin, for instance, stimulates the rate of
cell elongation, causes shoots to 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
hormones is somewhat analogous to that of certain
hormones in animals. 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 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.
Such a hierarchy may also exist in plants. Oligosaccharins
are fragments of the cell wall released
by enzymes: different enzymes release different
oligosaccharins. There are indications that pleiotropic
plant hormones may actually function by activating
the enzymes that release these other, more specific
chemical messengers from the cell wall.
Questions 128-133 refer to the passage above.
128. 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
(B) each hormone has various effects on plants ***Correct
(C) none of the hormones can function without
the others
(D) each hormone has different effects on different
kinds of plants
(E) each hormone works on only a small subset of a
cell's genes at any particular time
129. 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
(B) The complement of genes in each plant cell
(C) A subset of a plant cell's gene complement
(D) The five major hormones ***Correct
(E) The oligosaccharins
130. 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 ***correct
(B) To stimulate the walls of a particular cell to
produce other oligosaccharins
(C) To activate enzymes that release specific
chemical messengers from plant cell walls
(D) To duplicate the gene complement in a particular
plant cell
(E) To produce multiple effects on a particular
subsystem of plant cells
131. 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
(B) way in which hormones are produced by plants
(C) hierarchical nature of the functioning of plant
hormones
(D) differences among the best-known plant
hormones
(E) concept of pleiotropy as it is exhibited by plant
hormones ***Correct
132. 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 ***Correct
133. 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
(B) pinpoint functions of other plant hormones
(C) artificially control specific aspects of the
development of crops ***Correct
(D) alter the complement of genes in the cells of
plants
(E) alter the effects of the five major hormones on
plant development
All 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 small subset of the genes in a
particular kind of cell are expressed, or turned on,
at a given time. This is accomplished by a complex
system of chemical messengers that in plants
include hormones and other regulatory molecules.
Five major hormones have been identified: auxin,
abscisic acid, cytokinin, ethylene, and gibberellin.
Studies of plants have now identified a new class of
regulatory molecules called oligosaccharins.
Unlike the oligosaccharins, the five well-known
plant hormones are pleiotropic rather than specific;
that is, each has more than one effect on the
growth and development of plants. The five have
so many simultaneous effects that they are not
very useful in artificially controlling the growth of
crops. Auxin, for instance, stimulates the rate of
cell elongation, causes shoots to 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
hormones is somewhat analogous to that of certain
hormones in animals. 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 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.
Such a hierarchy may also exist in plants. Oligosaccharins
are fragments of the cell wall released
by enzymes: different enzymes release different
oligosaccharins. There are indications that pleiotropic
plant hormones may actually function by activating
the enzymes that release these other, more specific
chemical messengers from the cell wall.
Questions 128-133 refer to the passage above.
128. 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
(B) each hormone has various effects on plants ***Correct
(C) none of the hormones can function without
the others
(D) each hormone has different effects on different
kinds of plants
(E) each hormone works on only a small subset of a
cell's genes at any particular time
129. 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
(B) The complement of genes in each plant cell
(C) A subset of a plant cell's gene complement
(D) The five major hormones ***Correct
(E) The oligosaccharins
130. 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 ***correct
(B) To stimulate the walls of a particular cell to
produce other oligosaccharins
(C) To activate enzymes that release specific
chemical messengers from plant cell walls
(D) To duplicate the gene complement in a particular
plant cell
(E) To produce multiple effects on a particular
subsystem of plant cells
131. 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
(B) way in which hormones are produced by plants
(C) hierarchical nature of the functioning of plant
hormones
(D) differences among the best-known plant
hormones
(E) concept of pleiotropy as it is exhibited by plant
hormones ***Correct
132. 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 ***Correct
133. 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
(B) pinpoint functions of other plant hormones
(C) artificially control specific aspects of the
development of crops ***Correct
(D) alter the complement of genes in the cells of
plants
(E) alter the effects of the five major hormones on
plant development
