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Multiple Choice
Cytosine (C) makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine (T)?
A
8%
B
16%
C
21%
D
60%
Verified step by step guidance
1
Understand that DNA is composed of four types of nucleotides: adenine (A), thymine (T), cytosine (C), and guanine (G). In DNA, adenine pairs with thymine, and cytosine pairs with guanine.
Since cytosine (C) makes up 42% of the nucleotides, guanine (G) must also make up 42% because C pairs with G in equal amounts.
Calculate the total percentage of nucleotides that are either cytosine or guanine: 42% (C) + 42% (G) = 84%.
Subtract the percentage of cytosine and guanine from 100% to find the combined percentage of adenine and thymine: 100% - 84% = 16%.
Since adenine pairs with thymine in equal amounts, divide the remaining percentage equally between adenine and thymine: 16% / 2 = 8% for thymine.