Researchers of prebiotic chemical reactions have been testing the

Question

Researchers of prebiotic chemical reactions have been testing the theory that early life could have come about through RNA alone, gradually giving 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 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 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—methane, ammonia, water vapor, hydrogen, and carbon dioxide—and subjected the mixture to simulated lightning strikes. Within weeks the mixture contained the amino acids 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 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 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 polar ice caps, and the mixing of the two in the ocean.     1 
 1. The passage is primarily concerned with

A. explaining how life evolved from complex proteins
B. discussing how a theory on the origins of life has been tested and expanded upon
C. contemplating the evolution of life from non-complex proteins
D. describing how researchers solved the problem of creating life from RNA
E. reexamining an outdated theory on the development of DNA from seawater and lightning

2 
 2. It can be inferred from the passage that RNA molecules

A. are among the most basic structures known to man
B. are more complicated structures than are DNA molecules
C. can form a variety of structures and combinations
D. contain methane, ammonia, and water vapor, among other components
E. only function once charged by electrical impulses

3 
 3. 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.

4 
 4. Which of the following, if true, would most undermine Miller's argument ( Text in Red )?

A. Climatic conditions in the prebiotic world were inhospitable to the formation of life.
B. The polar ice caps in the prebiotic world covered more than one-quarter of the Earth's oceans.
C. Recent research indicates that uracil could not have existed in the prebiotic world.
D. Atmospheric pressure in the prebiotic world was much lower, leading to a near-absence of rain.
E. Prebiotic RNA from the middle of ancient land masses has been found to contain only small amounts of uracil and cytosine.

5 
 5. The author cites the experiment performed by Drs. Urey and Miller ( Text in Blue ) in order to

A. explain in further detail how they reached their conclusion
B. point out the methodological flaws in their research
C. show that methane, ammonia, water vapor, hydrogen and carbon dioxide were present in the prebiotic world
D. challenge the 1953 experiment as technologically inadequate to determine the role of RNA in the formation of life
E. support the thesis of Drs. Miller and Urey with conclusive scientific evidence

6 
 6. The passage suggests which of the following about the prebiotic chemical reactions that brought about life?

A. Although the reactions can be recreated in the laboratory, scientists cannot understand how they occurred in nature.
B. there is little direct evidence to prove scientists’ theories about such reactions.
C. While RNA plays a part in prebiotic chemical reactions, DNA is critical to the formation of life.
D. The presence of cytosine and uracil in the prebiotic ocean precluded the development of life.
E. Complex eco systems such as oceans and polar ice caps, are required for prebiotic chemical reactions to occur.

7 
 7. With which of the following statements about the origin of life would the author most likely agree?

A. Life in the prebiotic world must have derived from a combination of DNA and RNA.
B. without a greater understanding of the systems active in the prebiotic world, we cannot achieve a greater understanding of the origins of life.
C. Due to a paucity of data, the origins of life are poorly understood and difficult to explore.
D. While RNA is an important factor in enzyme production, it played a minor role in the creation of life.
E. Biologists play an important role in the study of prebiotic chemical reactions which formed the basis of human life.

PR CAT#2

nsrivastav064 · Accepted Answer

1st para: Researchers of prebiotic chemical reactions have been testing the theory - early life could have come about through RNA alone
2nd para - Using the example of experiment by Dr. Urey and Miller, the author supports that life could have begun without naturally occurring complex protein enzymes
3rd Para:Using the example of experiment proving the existence of requisite precursors:cytosine and uracil , the author confirms the validity of the RNA theory

Main idea of passage: The RNA theory has been tested by researchers of prebiotic chemical reactions. The author in the last para even provides another example of an experiment by Dr. Miller to establish the validity of "The RNA theory"

Q1. The passage is primarily concerned with

A. explaining how life evolved from complex proteins--  The evolution not explained 
B. discussing how a theory on the origins of life has been tested and expanded upon --  Based on my main idea above, this ans seems to be the most relevant choice 
C. contemplating the evolution of life from non-complex proteins  --Out of Scope 
D. describing how researchers solved the problem of creating life from RNA  -- The passage talks only about validating the RNA Theory  
E. reexamining an outdated theory on the development of DNA from seawater and lightning  --Out of Scope

2. It can be inferred from the passage that RNA molecules

A. are among the most basic structures known to man
B. are more complicated structures than are DNA molecules
C. can form a variety of structures and combinations --  2nd Para - Experiments conducted in 1983 showed that RNA molecules can split themselves and recombine in new arrangements 
D. contain methane, ammonia, and water vapor, among other components
E. only function once charged by electrical impulses

3. 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.  --2nd Para- Within weeks the mixture contained the amino acids necessary to build proteins. 
D. Cytosine and uracil formed in the sealed beaker.

4. Which of the following, if true, would most undermine Miller's argument (Text in Red)?

A. Climatic conditions in the prebiotic world were inhospitable to the formation of life.
B. The polar ice caps in the prebiotic world covered more than one-quarter of the Earth's oceans.
C. Recent research indicates that uracil could not have existed in the prebiotic world. -- The 3rd para mentions that -"He postulates that both substances could have been produced in the prebiotic ocean" This statement can be challenged if any research could prove that uracil/ cytosine could not exist at all in the prebiotic world 
D. Atmospheric pressure in the prebiotic world was much lower, leading to a near-absence of rain.
E. Prebiotic RNA from the middle of ancient land masses has been found to contain only small amounts of uracil and cytosine.

5. The author cites the experiment performed by Drs. Urey and Miller (Text in Blue) in order to

A. explain in further detail how they reached their conclusion-- The author introduces the experiment by Drs. Urey and Miller in the highlighted line. The following lines he describes the experiment in detail and later mentions that experiment successfully established that protein could be formed by the elements during the prebiotic world 
B. point out the methodological flaws in their research
C. show that methane, ammonia, water vapor, hydrogen and carbon dioxide were present in the prebiotic world
D. challenge the 1953 experiment as technologically inadequate to determine the role of RNA in the formation of life
E. support the thesis of Drs. Miller and Urey with conclusive scientific evidence

E. The experiment was conducted in a flask filled with protein enzymes.

6. The passage suggests which of the following about the prebiotic chemical reactions that brought about life?

A. Although the reactions can be recreated in the laboratory, scientists cannot understand how they occurred in nature.
B. there is little direct evidence to prove scientists’ theories about such reactions.  -- Though the passage mentions the experiments conducted by scientists, it doesn't highlight evidence to prove scientists’ theories.4th Para- The RNA theory was then generally accepted by most biologists, but the question remained:-- This provides evidence that there were few biologists who weren't satisfied with such experiments as well 
C. While RNA plays a part in prebiotic chemical reactions, DNA is critical to the form ation of life.
D. The presence of cytosine and uracil in the prebiotic ocean precluded the development of life.
E. Complex eco systems such as oceans and polar ice caps, are required for prebiotic chemical reactions to occur.

7. With which of the following statements about the origin of life would the author most likely agree?

A. Life in the prebiotic world must have derived from a combination of DNA and RNA.
B. without a greater understanding of the systems active in the prebiotic world, we cannot achieve a greater understanding of the origins of life .-- 1st para: Researchers of prebiotic chemical reactions have been testing the theory that early life could have come about through RNA alone 
C. Due to a paucity of data, the origins of life are poorly understood and difficult to explore.
D. While RNA is an important factor in enzyme production, it played a minor role in the creation of life.
E. Biologists play an important role in the study of prebiotic chemical reactions which formed the basis of human life.

Sajjad1994 · Answer

Official Explanation

3. According to the passage, which of the following is true of the experiment performed by Drs. Urey and Miller in 1953?

Explanation

The phrase according to the passage indicates that this is a retrieval question. The task of the question is indicated by the phrase  which of the following is true.  The subject of the question is  the experiment performed by Drs. Urey and Miller in 1953.  In order to answer the question, determine what the passage states about the subject and evaluate the answer choices, eliminating any choice which cannot be supported by the text. According to the passage,  That the protein could be formed by the elements at hand was 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—methane, ammonia, water vapor, hydrogen, and carbon dioxide—and subjected the mixture to simulated lightning strikes. Within weeks the mixture contained the amino acids necessary to build proteins.

Choice A: No.  The recycled words prebiotic and substances may make choice may seem appealing, but this choice is a reversal of facts in the passage. The passage states  Within weeks the mixture contained the amino acids necessary to build proteins , not that the mixture led to RNA itself.

Choice B: No.  The recycled language more than one dozen may make this choice seem appealing, since the passage references  13 of the 20 amino acids necessary for life.  However, the experiment yielding 13 amino acids is referred to as one further performed by Miller without reference to Urey, and cannot be supported as the same experiment.

Choice C:  Correct.   This choice is supported by the passage as it states  Within weeks the mixture contained the amino acids necessary to build proteins.

Choice D: No.  The recycled language cytosine and uracil may make this choice seem appealing, but this choice is recycled language. The passage mentions cytosine and uracil in reference to a different experiment.

Choice E: No.  This choice may seem appealing since the choice references  a flask filled with protein enzymes , but this choice is a reversal. The passage states that the experiment was performed in order to show  that life could have begun without naturally occurring complex protein enzymes, and that the flask was instead filled...with...methane, ammonia, water vapor, hydrogen, and carbon dioxide.

The correct answer is choice C.

Sajjad1994 · Answer

Official Explanation

6. The passage suggests which of the following about the prebiotic chemical reactions that brought about life?

Explanation

I will not say that the answer  choice (B)  is a perfect and strong answer choice but because the other four are so weak that they make  answer (B)  comparatively stronger. I will use POE to reach the answer. Let's read each choice one by one.

A. Although the reactions can be recreated in the laboratory,  scientists cannot understand  how they occurred in nature.

A strong language  "scientists cannot understand"  makes this option extreme and out of the race.

B. there is little direct evidence to prove scientists’ theories about such reactions.

Keep it for the moment and go further.

C. While RNA plays a part in prebiotic chemical reactions,  DNA is critical to the formation of life.

The second half part of this option is out of the scope of the passage.

D. The presence of cytosine and uracil in the prebiotic ocean precluded the development of life.

Same as  C.  Discussing something which cannot be validated with the help of the passage.

E. Complex ecosystems such as oceans and polar ice caps, are required for prebiotic chemical reactions to occur.

This is not something that the question is looking for.

Coming back to  (B), (B)  is better than the other four options. We can infer this option by reading very carefully the first half of the passage.

.......that early life  could have come  about through RNA alone, gradually giving 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 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 demonstrated as early as 1953, in an experiment by Drs. Urey and Miller.

The language used and especially the text in bigger size suggests that there is no 100% sure direct evidence to prove scientists’ theories about such reactions.

Hence:

Answer: B

Sajjad1994 · Answer

Explanation

7. With which of the following statements about the origin of life would the author most likely agree?

Explanation

(A)  is opposite, it is opposite to what is stated in the first paragraph. The word  "must"  is a big problem here, strike it out.

(B)  This seems relevant but not good enough at this stage so let's keep it and try to search for something better than this.

(C)  This is again distorting the information in the passage.  "Poorly understood"  is an issue here.

(D)  Minor or major role is not suggested in the passage.

(E)  Although  (E)  is correct according to the passage but this information is not sufficient to answer the question or one can say it is not relevant to the question.

By reading the whole passage we come to know that how life begins is still under investigation and there is no clear verdict available about that yet hence answer choice  (B)  fits best.

Answer: B

VerbalBot · Answer

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Researchers of prebiotic chemical reactions have been testing the

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