Which one of the following takes place in all eukaryotic organisms as a method of cellular defense?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → RNAi
Option (1) dsRNA — Incorrect. dsRNA is double-stranded RNA. It is the molecule that starts the defence: it binds to a complementary mRNA. It is a part of the process, not the process itself. Its source can be a virus with an RNA genome or a transposon.
Option (2) mRNA — Incorrect. mRNA (messenger RNA) carries the code of a gene to the ribosomes for making a protein. In this defence it is the target that gets silenced, not the defence.
Option (3) RNAi — Correct. RNA interference (RNAi) is the silencing of a specific mRNA by a complementary dsRNA that binds to it and stops its translation. Cells use it to block the genes of invading viruses and mobile genetic elements. It is used to make tobacco plants resistant to the nematode Meloidegyne incognitia.
Option (4) DNA — Incorrect. DNA is the genetic material of the cell. It is a molecule, not a method of defence.
NCERT Extract:
Biotechnological Applications in Agriculture – …
