Detailed Explanation:

Answer: Option 1 — 1, 2 and 4

RNA interference (RNAi) is a biological process where RNA molecules inhibit gene expression by neutralizing targeted mRNA molecules. This technology has gained popularity for its applications in gene silencing therapies, cancer treatment, and developing disease-resistant crops.

✅ Statement 1 – Correct: RNAi technology is extensively used in developing gene silencing therapies by targeting and reducing specific gene expressions to treat various diseases.
✅ Statement 2 – Correct: RNAi-based therapies are being actively researched and developed for cancer treatment by silencing genes responsible for tumor growth and proliferation.
❌ Statement 3 – Incorrect: RNAi is not used for hormone replacement therapies; it works by silencing genes rather than introducing hormones into the body.
✅ Statement 4 – Correct: RNAi technology is successfully applied in agriculture to produce crop plants resistant to viral pathogens by targeting and degrading viral RNA.

📝 Short Notes: RNA Interference (RNAi) Technology

• Definition: RNAi is a natural cellular process where double-stranded RNA molecules trigger the degradation of specific mRNA, thereby silencing gene expression.
• Discovery: First discovered in the 1990s by Andrew Fire and Craig Mello, who won the Nobel Prize in 2006 for their work.
• Mechanism: Small interfering RNAs (siRNAs) or micro RNAs (miRNAs) bind to complementary mRNA sequences, leading to their degradation or translational repression.
• Medical Applications: Used in treating genetic disorders, viral infections, and cancer by silencing disease-causing genes; several RNAi-based drugs are in clinical trials or approved.
• Agricultural Applications: Development of virus-resistant crops, enhanced nutritional content, and improved stress tolerance in plants.
• Limitations: Off-target effects, delivery challenges to specific tissues, and potential immune responses remain areas of ongoing research.