Name the source and type of cry genes used for incorporation into crops by biotechnologists. Explain, how have these genes brought beneficial changes in the genetically modified crops.
Bt toxin genes were isolated from the bacterium Bacillus thuringiensis and incorporated into several crops like cotton. The choice of the genes depends on the crop and the targeted pest, as most Bt toxins are insect group specific. The toxin is coded by a gene named cry, e.g. genes cry LAc and cry IIAb control cotton bollworms and that of cry LAb controls corn borer.