Statement I: When a crop expresses a cry gene, it typically gains resistance against a group of insects.

Statement II: Cry proteins derived from Bacillus thuringiensis exhibit toxicity towards the larvae of specific insects.

Both statements I and II are correct.

Statement I: When a crop expresses a cry gene, it gains resistance against a group of insects.

Explanation: The cry genes are a set of genes that produce insecticidal proteins known as Cry proteins. These genes are derived from the bacterium Bacillus thuringiensis (Bt), which naturally produces these proteins as part of its defense mechanism against certain insects. Scientists have genetically engineered some crops to express cry genes, which means the plants can produce Cry proteins on their own.

When a crop carries and expresses a cry gene, it synthesizes Cry proteins within its tissues. When insects, especially certain pest insects, feed on these genetically modified crops, the ingested Cry proteins become toxic to their digestive system. The Cry proteins target specific receptors in the insect gut, leading to the formation of pores in the gut lining, causing cell lysis, and eventually resulting in the death of the insect.

As a result, crops expressing cry genes gain protection against the targeted group of insects, which can be significant agricultural pests. This natural form of insect resistance provided by Cry proteins is considered an environmentally friendly alternative to chemical pesticides, as it specifically targets the pests without harming non-target organisms or the environment.

Statement II: Cry proteins produced from Bacillus thuringiensis are toxic to the larvae of certain insects.

Explanation: Bacillus thuringiensis (Bt) is a soil-dwelling bacterium that produces a group of insecticidal proteins called Cry proteins. These proteins are specifically toxic to the larvae (immature stages) of certain insects, including various caterpillars and other pest larvae.

When the Cry proteins are ingested by the susceptible insect larvae, they interact with specific receptors in the insect gut. This interaction triggers the activation of the Cry proteins, leading to the formation of pores in the gut lining. The formation of pores disrupts the gut's normal function, causing the insect to stop feeding and eventually leading to its death.

Because Cry proteins are highly selective in their toxicity, they target only certain insect species or groups of insects that possess the appropriate receptors in their digestive systems. This specificity is one of the key reasons why Bt-based insecticides, which contain Cry proteins, are widely used in agriculture and are considered environmentally friendly, as they pose minimal risk to non-target organisms, including humans and beneficial insects.