Assertion: "Cry" proteins are named so because they are crystal proteins.
Reason: In acidic environment of insect midgut "Cry" proteins are solubilized and then release toxic core fragments after proteolytic action.
Answer & explanation
Correct answer: option 3
The cry gene of Bacillus thuringiensis produces a protein, that forms crystalline inclusions i.e., is crystal in nature in the bacterial spores. Due to their crystal nature these proteins are named "cry" proteins and are responsible for the insecticidal activities of the bacterial strains. In alkaline environment of insect midgut "Cry" proteins are solubilized. Then to release core toxic fragments these proteins undergo proteolytic digestion.These toxins bind to receptors in brush border of midgut epithelial cells. As a result, brush border, membrane develop pores, most likely nonspecific in nature and cause influx of ions and water into the cells resulting in their swelling and eventual lysis.