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 pH of the insect gut.

In the light of the above statements, choose the correct answer from the options given below:

The correct option is Statement I is true but Statement II is false.

Let us analyze each statement step-by-step:

Analysis of Statement I:
Bt toxins are highly specific to certain groups of target insects (such as lepidopterans, coleopterans, and dipterans). These toxins are protein crystals encoded by specific genes called cry genes. For instance, the gene cryIAc codes for a toxin protein that specifically targets and controls cotton bollworms. Therefore, Statement I is true.

Analysis of Statement II:
Inside the bacterium Bacillus thuringiensis, the Bt toxin exists as an inactive, non-toxic protoxin crystal, which protects the bacterium itself from damage. When a susceptible insect ingests this protoxin, the crystal is solubilized and cleaved into its active form. This activation process occurs due to the alkaline pH of the insect's midgut, not an acidic pH. Because the statement incorrectly attributes the activation to an acidic pH, Statement II is false.

Conclusion:
Based on this biological reasoning, Statement I is true and Statement II is false.