Q.Explain the role of cry-genes in genetically modified crops.

Step 1. Bacillus thuringiensis (Bt), a soil bacterium, naturally produces crystal proteins called Cry (delta-endotoxin) proteins during sporulation, encoded by its cry genes; these toxins are specifically active against insects of the orders Lepidoptera, Diptera, Coleoptera and Hymenoptera.

Step 2. Scientists identified and isolated these cry genes and introduced them into the genome of crop plants using genetic engineering techniques, so that the transformed plant cells themselves begin expressing the Cry toxin protein.

Step 3. When a target insect pest (such as a bollworm) feeds on the leaves or tissue of such a genetically modified plant, it ingests the Cry toxin; in the insect's alkaline gut the toxin is activated and inserts into the gut-cell membrane, paralysing the digestive tract so the insect stops feeding and dies. …

Explain the source of the cry genes, how they are transferred into crops, and how the expre …

• Describing Bt spray as the mechanism instead of the gene being transferred directly into the plant's own genome. …