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Given below are two statements:
Statement $I$ : Bt toxins are insect group specific and coded by a gene cry $IAc$.
Statement $II$ : Bt toxin exists as inactive protoxin in B. thuringiensis. However, after ingestion by the insect the inactive protoxin gets converted into active form due to acidic $\mathrm{pH}$ of the insect gut.
In the light of the above statements, choose the correct answer from the options given below:
Both Statement $I$ and Statement $II$ are false
Statement $I$ is true but Statement $II$ is false
Statement $I$ is false but Statement $II$ is true
Both Statement $I$ and Statement $II$ are true
Solution
The correct answer is option ($2$) as specific Bt toxin genes were isolated from Bacillus thuringiensis and incorporated into the several crop plants such as cotton. 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 named cry. There are a number of them, for example, the proteins encoded by the genes cry $IAc$ and cry $\|Ab$ control the cotton bollworms, that of cry $IAb$ controls corn borer.
