2-nt 3' and blunt-ended siRNAs with RDR. Figure 13 shows the effects of high amplification through RDR and we can observe sustained gene silencing. The actual mRNA levels will however depend on the amplification rates and initial number of dsRNA molecules inserted into the cell.
Ghosh et al. BMC Genomics 2009 10(Suppl 1):S17 doi:10.1186/1471-2164-10-S1-S17