Sat 2015 Practice Test #1 Answer Explanations

Choice C is the best answer.
Lines 6-7 state that “Two of the possible 
bases — adenine and guanine — are purines,” and on the table the 
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Choices A, B, and D are incorrect because they do not state the 
percentages of both purines, adenine and guanine, in yeast DNA. 
QUESTION 29 
Choice A is the best answer.
The authors state: “We believe that the 
bases will be present almost entirely in their most probable forms. 
If this is true, the conditions for forming hydrogen bonds are more 
restrictive, and the only pairs of bases possible are: adenine with 
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that the pairs adenine/thymine and guanine/cytosine have notably 
similar percentages in DNA for all organisms listed. 
Choice B is incorrect. Although the choice of “Yes” is correct, the 
explanation for that choice misrepresents the data in the table. Choices C 
and D are incorrect because the table does support the authors’ proposed 
pairing of nitrogenous bases in DNA molecules. 
QUESTION 30 
Choice A is the best answer
because it gives the percentage of 
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authors’ proposal that possible pairings of nitrogenous bases are 
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Choices B, C, and D do not provide the best evidence for the answer 
to the previous question. Choice B (cytosine and thymine), Choice 
C (cytosine and adenine), and Choice D (guanine and adenine) are 
incorrect because they show pairings of nitrogenous bases that do not 
compose a similar percentage of the bases in sea urchin DNA. 

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QUESTION 31 
Choice D is the best answer.
The table clearly shows that the 
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Choices A and B are incorrect because the table shows that the 
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pairs with thymine but does not mention the variability of the base 
composition of DNA. 
QUESTION 32