The article by Tuschl et al. (1999) reports the development of a cell-free system from syncytial blastoderm Drosophila embryos that recapitulates key features of RNA interference (RNAi). The system demonstrates that double-stranded RNA (dsRNA) can specifically target and degrade target mRNAs, a process known as gene-specific, post-transcriptional silencing. The authors show that this interference is sequence-specific, promoted by dsRNA rather than single-stranded RNA, and requires a minimum length of dsRNA. Preincubation of dsRNA potentiates its activity, suggesting that it may be modified or associated with other factors in the lysate. The results indicate that RNAi can be mediated by sequence-specific processes in soluble reactions, providing a valuable tool for studying gene function in various organisms.The article by Tuschl et al. (1999) reports the development of a cell-free system from syncytial blastoderm Drosophila embryos that recapitulates key features of RNA interference (RNAi). The system demonstrates that double-stranded RNA (dsRNA) can specifically target and degrade target mRNAs, a process known as gene-specific, post-transcriptional silencing. The authors show that this interference is sequence-specific, promoted by dsRNA rather than single-stranded RNA, and requires a minimum length of dsRNA. Preincubation of dsRNA potentiates its activity, suggesting that it may be modified or associated with other factors in the lysate. The results indicate that RNAi can be mediated by sequence-specific processes in soluble reactions, providing a valuable tool for studying gene function in various organisms.