Question

Name the cry-genes that control cotton bollworm and corn borer respectively.

Answer 1

Hint: Cry gene codes for the Bt toxin. Bt cotton was created through the addition of genes encoding toxin crystals belong to the Cry group of endotoxin. Cry I Ac gene and cry II Ab gene kill the cotton bollworms while cry I Ab kills corn borer.

Complete answer:
The Bt toxin is encoded by a gene named cry gene. There are a number of genes. They are isolated from Bacillus thuringiensis and incorporated into several crop plants such as cotton. The selection of genes totally depends upon the crop and targeted pest, as most Bt toxins are insect-specific groups. Two groups of cry genes, cry I Ac and cry II Ab have been incorporated in cotton. The genes cry I Ac and cry II Ab kill the cotton bollworms. Similarly, cry I Ab has been incorporated in Bt corn to protect the same from corn borer.
The activated Bt toxin provides resistance to plants against lepidopteran, coleoptera and diptera pests. It acts on the surface of the midgut epithelium of the insects and causes swelling and then cell lysis, which eventually leads to the death of the insects. Since these toxins are insect specific (insecticidal), they do not harm the crops and humans.

Note:
Various strains of the bacterium Bacillus thuringiensis produce many different Bt toxins, each harmful to different insects. Bt toxins are mostly insecticidal to the larvae beetles, moths, butterflies, cotton bollworms and ghtu flies but they are harmless to other forms of life. Bt cotton was created through the addition of genes encoding toxin crystals in the Cry endotoxin.