Multiple Choice
Which type of interaction contributes the most to holding the two strands of DNA together in the double helix?
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7. DNA and Chromosome Structure
DNA Structure
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Which of the following is NOT a nucleotide found in DNA?
A
Cytosine
B
Guanine
C
Adenine
D
Uracil
Verified step by step guidance1
Recall that DNA is composed of four main nucleotides: Adenine (A), Thymine (T), Cytosine (C), and Guanine (G). Each nucleotide consists of a nitrogenous base, a sugar (deoxyribose), and a phosphate group.
Identify the nitrogenous bases listed in the problem: Cytosine, Guanine, Adenine, and Uracil.
Understand that Uracil is a nitrogenous base found in RNA, not DNA. In RNA, Uracil replaces Thymine and pairs with Adenine.
Compare the bases to confirm which are found in DNA and which are not. Since Cytosine, Guanine, and Adenine are all DNA bases, Uracil is the one that is NOT found in DNA.
Conclude that the correct answer is Uracil because it is exclusive to RNA and does not occur in the nucleotide composition of DNA.
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