In RNAi, the genes are silenced using
(a) dsRNA (b) ssDNA
(c) ssRNA (d) dsDNA.
Answer (a) : RNAi or RNA interference is a novel strategy which prevents the infection by nematode Meloidogyne incognita in the roots of tobacco plants. RNAi involves silencing of specific mRNA. Using Agrobacterium vectors, nematode specific genes are introduced into the host plant (tobacco plant). The introduction of DNA is such that it produces both sense and anti-sense RNA in the host cells. These two RNAs, being complementary to each other form a dsRNA (double stranded RNA), that initiates RNAi by first forming siRNA (small interfering RNAs). The siRNA first unwinds and then binds to specific complementary mRNA molecules of the nematode. These sites are then cut by RISC (RNA-induced silencing complex), thereby destroying mRNA of host. Hence, no toxin proteins are synthesised.
