Step 1: Definition.
Bio-fertilizers are living microorganisms which, when applied to seeds, plant surfaces, or soil, promote growth by increasing the availability of essential nutrients to plants.
Step 2: Examples of bio-fertilizers.
\[\begin{array}{rl} \bullet & \text{Rhizobium: Symbiotic bacteria in root nodules of legumes; fix atmospheric nitrogen.} \\ \bullet & \text{Azotobacter and Azospirillum: Free-living nitrogen-fixing bacteria.} \\ \bullet & \text{Cyanobacteria (Blue-Green Algae like Anabaena, Nostoc): Fix nitrogen in paddy fields.} \\ \bullet & \text{Mycorrhizal fungi: Enhance phosphorus and water absorption.} \\ \end{array}\]
Step 3: Role in food production.
\[\begin{array}{rl} \bullet & \text{Increase soil fertility naturally without chemical fertilizers.} \\ \bullet & \text{Promote sustainable agriculture by reducing pollution.} \\ \bullet & \text{Improve crop yield, especially in cereals, legumes, and paddy.} \\ \bullet & \text{Cost-effective and eco-friendly compared to synthetic fertilizers.} \\ \end{array}\]
Conclusion.
Bio-fertilizers are essential for eco-friendly, sustainable agriculture and play a vital role in ensuring long-term food security.
Answer the following questions:
(a) [(i)] Explain how some strains of Bacillus thuringiensis produce proteins that kill certain insects such as lepidopterans but do not kill the Bacillus.
[(ii)] How is the above mechanism exploited for the production of Bt cotton plant by biotechnologists?
(b) [(i)] Explain how the amplification of gene of interest is done using PCR.
[(ii)] State two applications of the desired amplified fragment of DNA.
The basic scheme of the essential steps involved in the process of recombinant DNA technology is summarised below in the form of a flow diagram. Study the given flow diagram and answer the questions that follow.
(a) What is the technical term used for Step 4 in the above process?
(b) Which of the given two combinations of restriction enzyme should be used in Step 1? Justify your answer.
(i) EcoR I to cut the plasmid and Hind III to cut the alien DNA.
(ii) EcoR I to cut both the plasmid and alien DNA.