Abstract
Gene silencing is a general term describing epigenetic process of gene regulation. Then term silencing is generally used to describe the "switching off" of gene by a mechanism other than genetic modification. That is a gene which would be expressed (turn on) under switched off by mechanism in the cell. Also, may be part of an ancient immune system protecting from infection DNA element.
Pioneering observation on PTGs/ RNAi were reported in plant but later on RNAi-related events were described in almost all eukaryotic organism, including Protozoa, nematodes, insect, parasite and human cell line.
