Multiple choice

In a solution of nucleotides, made from a ground-up segment of DNA, adenine makes up 33% of the solution. What percentage of the solution would be guanine?

  1. 17%

  2. 27%

  3. 24%

  4. 33%
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A Correct answer
Explanation

According to Chargaff's rules, in double-stranded DNA, adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C). If adenine is 33%, then thymine is also 33%. This accounts for 66% of the nucleotides. The remaining 34% must be guanine + cytosine in equal proportions, so guanine is 17% and cytosine is 17%.

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