BRAINCAKEsiRNA
Small interfering RNA (siRNA) is short, double-stranded RNA, about 21 to 23 nucleotides long, that silences a specific gene by causing its mRNA to be destroyed before it can be translated. This is called RNA interference (RNAi). It controls gene expression after transcription.
How siRNA silences a gene
1. A long molecule of double-stranded RNA is present in the cell. It may come from a virus or be introduced by scientists.
2. An enzyme called Dicer cuts the long double-stranded RNA into siRNA molecules.
3. The siRNA is loaded into a protein complex called RISC (RNA-induced silencing complex). The two strands separate and one strand is kept.
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All 39 lessons in Gene Expression · All Edexcel A-level Biology topics