Read the following passage carefully and answer the given questions.
Some strains of Bacillus thuringiensis produce proteins that kill certain insects such as lepidopterans (tobacco budworm, armyworm), coleopterans (beetles) and dipterans (flies, mosquitoes). B. thuringiensis forms protein crystals during a particular phase of their growth. Transgenic animals that produce useful biological products can be created by the introduction of the portion of DNA (or genes) which codes for a particular product such as human protein (α-1-antitrypsin) used to treat emphysema. In 1997, the first transgenic cow, Rosie, produced human protein-enriched milk (2.4 grams per litre). The milk contained the human alpha-lactalbumin and was nutritionally a more balanced product for human babies than natural cow-milk. A nematode Meloidegyne incognitia infects the roots of tobacco plants and causes a great reduction in yield. A novel strategy was adopted to prevent this infestation which was based on the process of RNA interference (RNAi). This method involves silencing of a specific mRNA due to a complementary dsRNA molecule that binds to and prevents translation of the mRNA (silencing). Biopiracy is the term used to refer to the use of bio-resources by multinational companies and other organisations without proper authorisation from the countries and people concerned without compensatory payment. ELISA is based on the principle of antigen-antibody interaction. Infection by pathogen can be detected by the presence of antigens (proteins, glycoproteins, etc.) or by detecting the antibodies synthesised against the pathogen.
mRNA silencing through RNA interference (RNAi) refers to the:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Prevention of translation of mRNA
In RNA interference (RNAi) a complementary double-stranded RNA binds to a particular mRNA. The passage says this prevents translation of the mRNA; this is called silencing. It was used to make tobacco plants resistant to the nematode Meloidegyne incognitia.
Option (1) Prevention of translation of mRNA — Correct. In RNA interference, a complementary dsRNA binds to a specific mRNA, so that mRNA is silenced: it is not translated into protein. This is a cellular defence in all eukaryotes.
Option (2) Prevention of transcription of mRNA — Incorrect. Transcription is making RNA from DNA; RNAi acts on mRNA that is already made.
Option (3) Prevention of replication of mRNA — Incorrect. Replication is copying DNA; mRNA does not replicate in the cell.
Option (4) Prevention of reverse transcription of mRNA — Incorrect. Reverse transcription is making DNA from RNA, as retroviruses do; it is not what RNAi blocks.
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.