*2.3.2. Sequence feature for efficient RISC entry*

siRNA guide strands with low energy at 5' end are favored for entering the RISC complex. So, presence of at least three (A/U)s in the seven nucleotides at the 3' end of the sense strand is preferable.

#### *2.3.3. siRNA duplex stability*

Target sites with low GC content (generally less than 55%) has a greater potential for being functional siRNA site, as too high GC content can impede the loading of siRNAs into RISC complex. Also, too low GC content is not favourable because too low GC content can destabilize the siRNA duplex and reduce their affinity to target mRNA binding. Analysis of effective siRNAs showed G/C content between 35% and 60% is most favorable.


**Table 1.** Position specific nucleotide composition prefered in functional siRNAs
