In a double-stranded DNA molecule 20 percent of the bases are adenine. What percentage are guanine?
Answer and explanation
Correct answer: B. 30%
- Step 1: A pairs with T, so thymine is also 20%.
- Step 2: A + T = 40%; the remaining 60% is G + C, shared equally, so G = 30%.
Answer
30%.
Why not the others: 20%: guanine was assumed to be as common as adenine. 60%: this is the combined percentage of guanine and cytosine. 70%: the percentages were added.
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