DNA vs RNA: what's the difference?
A-Level Biology
Both are nucleic acids built from nucleotides, but they differ in sugar, bases, structure and job.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
DNA vs RNA — side by side
| DNA | RNA | |
|---|---|---|
| Sugar | Deoxyribose | Ribose |
| Bases | A, T, C, G | A, U, C, G (uracil replaces thymine) |
| Strands | Double-stranded helix | Single-stranded |
| Length/stability | Long and stable (stores genetic code) | Shorter, less stable (carries/decodes it) |
| Function | Stores genetic information | mRNA carries code; tRNA/rRNA build proteins |
Exam tip — how to tell them apart: RNA = Ribose + Uracil + single strand. DNA = Deoxyribose + Thymine + double strand.
Common trap: Uracil (not thymine) is the RNA base — a very common slip.
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