Answer to Question #25802 in Molecular Biology for Alesha
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.