Question 1

What is the cry gene in Bt cotton?

Accepted Answer

The cry gene is the introduced DNA sequence that encodes a toxin protein from Bacillus thuringiensis. The gene is part of the cotton genome, while the plant cells produce the encoded Bt toxin protein.

Question 2

How does Bt cotton protect itself from insect pests?

Accepted Answer

Cotton cells produce the Bt toxin protein as an inactive protoxin. When an insect pest feeds on the plant, the ingested protein is activated in the pest alkaline gut and kills the pest, reducing damage to the crop.

Question 3

Is the cry gene itself the toxin?

Accepted Answer

No. The cry gene is DNA that contains the coding information for the toxin protein. The toxin is the protein produced when the cotton cell expresses the introduced gene.

Question 4

Where is Bt protoxin activated?

Accepted Answer

The inactive Bt protoxin produced by the cotton plant is activated in the alkaline gut of an insect pest after ingestion. This means the plant-made protoxin is not the same form that kills the pest until it reaches the insect gut.

Question 5

What does switching the Bt gene OFF in the model mean?

Accepted Answer

It represents a plant state in which the introduced cry gene is not being expressed. The cotton cells therefore do not produce the Bt toxin protein, and the model allows insect-pest feeding to return so the student can compare protected and unprotected states.

Bt Cotton Defence Lab — How a Transgenic Crop Protects Itself

About this lab

Practice