Question

Which statement is correct about Bt cotton:-
(a)Contains a gene from jellyfish which makes it glow in the dark
(b)It contains a gene from Bacillus bacteria which is not useful to plants
(c)It contains a gene from Bacillus bacteria which kill the pests
(d)It contains a gene from Bacillus bacteria which kill other plants

Answer 1

Hint: Bt cotton is a genetically modified plant to be able to kill insects such as lepidopterans (tobacco budworm, armyworm), coleopterans (beetles), and dipterans (flies, mosquitoes). But the plant is not harmed as the toxin is present in the inactive stage inside the plant.

Complete answer:
Bt cotton contains a gene from the bacterium Bacillus thuringiensis which is used to kill the pests that feed on this plant. The Bt toxin gene has been cloned from the bacteria and been expressed in the cotton plant to provide it resistance against insects without the need for insecticides. Due to this, the dependence of insecticides decreases, thus resulting in less pollution of the soil by these non-biodegradable chemicals. Many plants have been introduced with this gene such as Bt corn, Bt rice, Bt tomato, Bt soybean, etc.

Additional Information:
 Let us look in detail at how the Bt toxin works.
-The Bt toxin gene works by producing protein crystals that contain a toxic insecticidal protein.
-This Bt toxin exists as inactive Pro-toxins inside the plant and thus does not harm the plant.
-The moment an insect feeds on a plant, this toxin is also ingested by that insect.
-Once the toxin enters the gut, it gets converted into an active form by the alkaline pH of the gut which solubilizes the crystals.
-The activated toxin binds to the surface of the epithelial cells of the midgut and creates pores in it.
-This leads to swelling and lysis eventually followed by the death of the insect.
So, the correct option is ‘It contains a gene from Bacillus bacteria which kill the pests’.

Note:
 -Specific Bt toxin genes have been isolated from the bacterium Bacillus thuringiensis.
-The toxin genes are known as cry genes.
-The cry genes cryIAc and cryIIAb kill cotton bollworms whereas the cryIAb kills the corn borer.