Multiple Choice
Which of the following sequences represents a strand of RNA bases?
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7. DNA and Chromosome Structure
RNA
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Which of the following characteristics of Figure 1 best indicates that the fragment is RNA and not DNA?
A
The double-stranded helical structure
B
The use of adenine pairing with thymine
C
The presence of deoxyribose sugar in the backbone
D
The presence of uracil bases instead of thymine
Verified step by step guidance1
Understand the fundamental chemical differences between RNA and DNA. RNA contains the sugar ribose, while DNA contains deoxyribose, which lacks one oxygen atom compared to ribose.
Recall the nitrogenous bases present in each nucleic acid: DNA uses adenine (A), thymine (T), cytosine (C), and guanine (G), whereas RNA uses adenine (A), uracil (U), cytosine (C), and guanine (G).
Identify that the presence of uracil (U) instead of thymine (T) is a key distinguishing feature of RNA, as thymine is replaced by uracil in RNA molecules.
Note that the double-stranded helical structure and adenine pairing with thymine are characteristics typical of DNA, not RNA, so these features do not indicate the fragment is RNA.
Conclude that the best indicator that the fragment is RNA is the presence of uracil bases instead of thymine, which directly reflects the unique base composition of RNA.
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