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rashmi.kaushal
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Editor's note: The Princeton Review update as of August 2010
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1 Researchers of prebiotic chemical
reactions have been testing the theory
that early life could have come about
through RNA alone, gradually giving
5 way to a world in which RNA and DNA
work together.
Experiments conducted in 1983
showed that RNA molecules can split
themselves and recombine in new
10 arrangements, leading to the conclusion
that life could have begun without
naturally occurring complex protein
enzymes. That the protein could be
formed by the elements at hand was
15 demonstrated as early as 1953, in an
experiment by Drs. Urey and Miller.
They filled a sealed flask with
substances considered to have been
plentiful in the earth's prebiotic state-
20 methane, ammonia, water vapor,
hydrogen, and carbon dioxide-and
subjected the mixture to simulated
lightning strikes. Within weeks the
mixture contained the amino acids
25 necessary to build proteins. By
experimenting further, Dr. Miller was
able to create 13 of the 20 amino acids
necessary for life.
The RNA theory was then generally
30 accepted by most biologists, but the
question remained: how could RNA
exist without its requisite precursors,
cytosine and uracil? This problem now
appears to have been solved, again by
35 Dr. Miller. He postulates that both
substances could have been produced
in the prebiotic ocean through a process
that entails the evaporation of sea
water, the freezing of sea water in the
40 polar ice caps, and the mixing of the two
in the ocean.
According to the passage, which of the following is true of the experiment performed by Drs. Urey and Miller in 1953?
A)RNA was fabricated out of simple prebiotic substances.
B)More than one dozen significant amino acids were synthesized.
C)The experiment took several weeks to complete.
D)Cytosine and uracil formed in the sealed beaker.
E)The experiment was conducted in a flask filled with protein enzymes.
What should be the correct Answer ? Why is not B ?
C
Get The Princeton Review discounts: Latest The Princeton Review Course promo codes https://www.beatthegmat.com/mba/partner ... t-discount
---------
1 Researchers of prebiotic chemical
reactions have been testing the theory
that early life could have come about
through RNA alone, gradually giving
5 way to a world in which RNA and DNA
work together.
Experiments conducted in 1983
showed that RNA molecules can split
themselves and recombine in new
10 arrangements, leading to the conclusion
that life could have begun without
naturally occurring complex protein
enzymes. That the protein could be
formed by the elements at hand was
15 demonstrated as early as 1953, in an
experiment by Drs. Urey and Miller.
They filled a sealed flask with
substances considered to have been
plentiful in the earth's prebiotic state-
20 methane, ammonia, water vapor,
hydrogen, and carbon dioxide-and
subjected the mixture to simulated
lightning strikes. Within weeks the
mixture contained the amino acids
25 necessary to build proteins. By
experimenting further, Dr. Miller was
able to create 13 of the 20 amino acids
necessary for life.
The RNA theory was then generally
30 accepted by most biologists, but the
question remained: how could RNA
exist without its requisite precursors,
cytosine and uracil? This problem now
appears to have been solved, again by
35 Dr. Miller. He postulates that both
substances could have been produced
in the prebiotic ocean through a process
that entails the evaporation of sea
water, the freezing of sea water in the
40 polar ice caps, and the mixing of the two
in the ocean.
According to the passage, which of the following is true of the experiment performed by Drs. Urey and Miller in 1953?
A)RNA was fabricated out of simple prebiotic substances.
B)More than one dozen significant amino acids were synthesized.
C)The experiment took several weeks to complete.
D)Cytosine and uracil formed in the sealed beaker.
E)The experiment was conducted in a flask filled with protein enzymes.
What should be the correct Answer ? Why is not B ?
C
