RNA could precede DNA and proteins because one nucleotide polymer can store inherited information, copy sequences, fold into catalysts, and still catalyse peptide formation in ribosomes.
Coverage 2012–2025 · Updated 15 Jul 2026
RNA is a plausible first genetic material because its nucleotide sequence can store information and some folded RNA molecules can catalyse reactions.
RNA can be copied, allowing heredity and variation, while catalytic RNAs called ribozymes can accelerate reactions. RNA could therefore have performed roles now divided between DNA and protein enzymes.
Use two independent properties in the argument: replication/information storage and catalytic activity. Both are needed to explain why RNA is a stronger candidate than a molecule that performs only one job.
Ribosomal RNA still catalyses peptide-bond formation in the ribosome, providing a modern example of RNA acting catalytically.
The RNA-world model is a supported hypothesis, not a direct observation of the first genetic system; it must also explain how RNA formed and persisted prebiotically.
This objective is assessed through structured response, commonly using Outline / State / Explain.
Outline / State / Explain / Identify / Describe
Build the answer around this relationship: RNA nucleotide sequences can store hereditary information.
Giving only RNA's informational role and omitting its catalytic activity.
Representative question
Describe the structure of RNA and the evidence that it was the first genetic material used to store information.
A2.1 is usually tested as a connected argument, not as isolated facts. A strong answer builds a chain: early Earth conditions made abiotic organic synthesis plausible; origin models require small molecules, polymers, self-replication, and membranes; experiments and models support parts of the chain; LUCA, dating, and vents provide later evidence and constraints. The highest-scoring habit is to say “supports” when evidence supports, and avoid saying “proves” when it does not.
