discuss rnai from start of transcript to degradation
The process of RNAi begins with the action ofthe enzyme Dicer, which cuts the long molecules of double-stranded RNA (dsRNA)into short fragments about 21-25 nucleotides, called siRNA. One of the two strands of each fragment called "guided", the single-stranded RNA is then included in the RNA-protein complex RISC. As a result of the activity of RISC single-stranded RNA fragment is connected with a complementary sequence of mRNA molecules and causes the cutting mRNA by Argonaute protein or inhibition of translation and / or mRNA deadenylation. These events lead to the suppression of expression (silencing) of the corresponding gene, which efficiency is limited by the concentration of molecules of small RNA - siRNA and micro RNA.