Fig. 1.

The primary forms of genetic material delivered to cells and the steps they undergo to regulate gene expression. A) pDNA is delivered and subsequently transcribed and translated via host cell machinery to upregulate target protein production. B) mRNA is delivered and subsequently translated to upregulate target protein production. C) RNAi molecules such as siRNA or miRNA are delivered as double stranded RNA. In both forms of RNAi the passenger strand (yellow) is discarded and the guide strand (green) is retained in the RISC complex. The guide strand directs the RISC complex to a target host mRNA sequence. siRNA binds to a fully complimentary target mRNA sequence to downregulate host mRNA translation. miRNA only needs to bind to a partially complementary target mRNA sequence to downregulate host mRNA translation.