BRAINCAKERNA Interference (siRNA and miRNA)
Gene expression can also be controlled after transcription. In eukaryotes and some prokaryotes, translation of the mRNA produced from target genes can be inhibited by RNA interference (RNAi). RNAi uses small, double-stranded RNA molecules to stop mRNA being translated.
Small interfering RNA (siRNA)
1. An enzyme cuts double-stranded RNA into short pieces called siRNA.
2. One strand of the siRNA combines with an enzyme (part of a protein complex).
3. The siRNA strand guides the enzyme to an mRNA molecule with a complementary base sequence, where it binds by base pairing.
4. The enzyme cuts the mRNA into fragments, so it cannot be translated. The fragments are then broken down.
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More in Control of Gene Expression
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All 18 lessons in Control of Gene Expression · All AQA A-level Biology topics