True regarding DDT is: September 2007

Ans. A: Synthetic insecticide DDT is an organochlorine, similar in structure to the insecticide methoxychlor and the acaricide dicofol. It is a highly hydrophobic, colorless, crystalline solid with a weak, chemical odor. It is nearly insoluble in water but has a good solubility in most organic solvents, fats, and oils. DDT does not occur naturally, but is produced by the reaction of chloral (CC13CH0) with chlorobenzene (C6H5C1) in the presence of sulfuric acid, which acts as a catalyst. In insects it opens sodium ion channels in neurons, causing them to fire spontaneously, which leads to spasms and eventual death. Insects with ceain mutations in their sodium channel gene are resistant to DDT and other similar insecticides. DDT resistance is also conferred by u p-regulation of genes expressing cytochrome P450 in some insect species.