The toxin proteins isolated from Bacillus thuringiensis, coded by which of the following genes would control cotton bollworms and corn borer, respectively ?

The bacterium Bacillus thuringiensis (Bt) produces a variety of crystal (Cry) proteins that are toxic to specific insect orders. Each Cry protein is encoded by a distinct gene (e.g., cryIAc, cryIAb, cryIIAb) and has a characteristic spectrum of activity.

To determine which genes control cotton bollworms and corn borer, we consider the known host range of the Cry proteins:

CryIAc – This Cry protein belongs to the Cry1 family and is highly effective against lepidopteran pests, especially cotton bollworms (Helicoverpa armigera). Laboratory and field studies have repeatedly shown that CryIAc expressed in transgenic cotton confers strong resistance to bollworm damage.

CryIAb – Also a member of the Cry1 family, CryIAb exhibits potent activity against several lepidopteran species, including the Asian corn borer (Ostrinia furnacalis). CryIAb has been utilized in genetically engineered corn to protect against this borer.

Therefore, the pair of genes that encode toxin proteins targeting cotton bollworms first and corn borer second is cryIAc (cotton bollworm) and cryIAb (corn borer).

This matches the provided correct option, confirming that the answer is cryIAc and cryIAb.