 Sequence-specific activation of gene expression refers to CRISPR activation (CRISPRa).Based on the bacterial genetic immune system - CRISPR (clustered regularly interspaced short palindromic repeats) pathway, 
the technique provides a complementary approach to RNA interference.The difference between CRISPRi and RNAi, though, is that CRISPRi regulates gene expression primarily on the transcriptional level, while RNAi controls genes on the mRNA level.