Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): The choice of cry gene introduced into a crop plant depends on the crop and the targeted pest.
Reason (R): Most Bt toxins are insect-group specific.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Both (A) and (R) are true and (R) is the correct explanation of (A).
Assertion (A): The choice of cry gene introduced into a crop plant depends on the crop and the targeted pest. — True. A is about how the gene is chosen. For cotton, whose pest is the bollworm, genes such as cryIAc and cryIIAb are used; for corn, whose pest is the corn borer, cryIAb is used.
Reason (R): Most Bt toxins are insect-group specific. — True. R is about what the toxins act on. Each Bt toxin kills only one group of insects, for example lepidopterans, coleopterans or dipterans.
Why R explains A? A toxin that acts on one group of insects will protect a crop only if that group is the crop’s pest. So the gene has to be picked to match the pest of each crop. The specificity in R is the cause of the choice described in A, and R is the correct explanation of A.
NCERT Extract:
Biotechnological Applications in Agriculture – “… The choice of genes depends upon the crop and the targeted pest, as most Bt toxins are insect-group specific. The toxin is coded by a gene cryIAc named cry. There are a number of them, for example, the proteins encoded by the genes cryIAc and cryIIAb control the cotton bollworms, that of cryIAb controls corn borer.”