Multiple Choice
In DNA structure, what chemical components form the repeating backbone of the DNA double helix?
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7. DNA and Chromosome Structure
DNA Structure
Multiple Choice
Which set correctly lists the nitrogenous bases found in DNA?
A
Adenine, thymine, cytosine, and uracil
B
Adenine, thymine, cytosine, and guanine
C
Adenine, uracil, cytosine, and guanine
D
Thymine, uracil, cytosine, and guanine
Verified step by step guidance1
Step 1: Understand that DNA (deoxyribonucleic acid) is composed of four nitrogenous bases that pair specifically to form the double helix structure.
Step 2: Recall the two categories of nitrogenous bases: purines and pyrimidines. In DNA, the purines are adenine (A) and guanine (G), and the pyrimidines are cytosine (C) and thymine (T).
Step 3: Recognize that uracil (U) is a nitrogenous base found only in RNA, replacing thymine during transcription, and is not present in DNA.
Step 4: Therefore, the correct set of nitrogenous bases in DNA includes adenine, thymine, cytosine, and guanine.
Step 5: Summarize that the correct answer excludes uracil and includes thymine, confirming the set: adenine, thymine, cytosine, and guanine.
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