RNA Interference (RNAi)
RNA குறுக்கீடு (RNAi)
RNA interference is not just a mechanism; it is the cell's immune system against invasive genetic material. If you confuse dsRNA with mRNA, you lose marks. Remember: silencing is not deletion, it is prevention of translation.
The idea
RNAi occurs in all eukaryotic organisms as a method of cellular defense. It involves silencing a specific mRNA due to a complementary dsRNA molecule that binds to and prevents translation of the mRNA. The source of this complementary RNA could be from an infection by viruses having RNA genomes or mobile genetic elements (transposons) that replicate via an RNA intermediate.
Why it matters
It serves as a natural defense against viral infections and mobile genetic elements (transposons) that replicate via RNA intermediates.
NEET lens
NEET focuses on the source of dsRNA and the specific nematode example. Memorize the organism name: Meloidogyne incognita. Do not confuse the vector (Agrobacterium) with the mechanism (RNAi). Expect questions on the 'silencing' process; it is a post-transcriptional gene regulation event.
Clinical significance
In agriculture, RNAi is used to protect tobacco plants from the nematode Meloidogyne incognita. By introducing nematode-specific genes via Agrobacterium vectors, the plant produces dsRNA that silences essential nematode genes. Without this, the parasite would colonize the roots and destroy the crop yield.
Introduction
RNA interference (RNAi) is a method of cellular defence in all eukaryotic organisms. It silences a specific mRNA by a complementary double-stranded RNA (dsRNA) molecule that binds to and prevents translation of the mRNA.
Core concept
Application (NCERT): pest-resistant plants — a nematode Meloidogyne incognita infects the roots of tobacco plants and causes a great reduction in yield. Using Agrobacterium vectors, nematode-specific genes were introduced into the host plant in such a way that it produced both sense and anti-sense RNA in the host cells. These two RNAs, being complementary, formed dsRNA, which initiated RNAi and silenced the specific mRNA of the nematode. The parasite could not survive in the transgenic host expressing the specific interfering RNA, so the plant was protected. The source of the complementary RNA could be from an infection by viruses having RNA genomes or mobile genetic elements (transposons) that replicate via an RNA intermediate.
Go deeper
RNAi is gene silencing at the mRNA level — the gene is still there but its message is destroyed or blocked.
From Class 10
Some plants can be made to produce a matching RNA that 'switches off' an essential gene of the pest that attacks them.