Biology · Biotechnology and Its Applications · NEET
Bt cotton is resistant to INSECT PESTS, chiefly lepidopteran bollworms. It is NOT the strategy used against nematodes. Making plants nematode-resistant (for example against Meloidogyne incognita in tobacco roots) uses RNA interference (RNAi), a completely different method. NEET loves to swap these two, so remember: Bt = insect pest resistance; RNAi = nematode resistance.
A cry gene (a Bt toxin gene) is taken from the soil bacterium Bacillus thuringiensis and inserted into cotton. The proteins encoded by cryIAc and cryIIAb control the cotton bollworms, while cryIAb controls corn borer. So for cotton specifically, cryIAc is the gene to remember.
No. Bt toxins are insect-group specific. A given Bt protein kills only certain insect groups, such as lepidopterans (bollworms, budworms), coleopterans (beetles) or dipterans (flies, mosquitoes). This is why different cry genes are used for different target pests, and why Bt cotton mainly protects against bollworms.
Because the plant itself produces the Bt toxin inside its tissues. When a bollworm eats the plant, the toxin activates in its gut and kills it. The crop carries its own bio-insecticide, so the farmer does not need to spray as much chemical insecticide.
Yes. Bt cotton is a genetically modified organism (GMO) because a foreign gene (the cry gene from Bacillus thuringiensis) has been added to the cotton plant using genetic engineering. It is one of the standard NCERT examples of a GM crop, along with Bt corn, Flavr Savr tomato and Golden rice.
Bt cotton variety that was developed by the introduction of toxin gene of Bacillus thuringiensis (bt) is resistant to:
The toxin proteins isolated from Bacillus thuringiensis, coded by which of the following genes would control cotton bollworms and corn borer, respectively?
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Bt cotton is cotton that has been given a gene from the bacterium Bacillus thuringiensis. This gene makes the plant produce a toxin that kills insect pests like bollworms, so the plant protects itself.
Bt stands for Bacillus thuringiensis, the soil bacterium whose cry gene (toxin gene) is transferred into the cotton plant.
cryIAc (and cryIIAb) control cotton bollworms, so cryIAc is the key gene for Bt cotton. cryIAb is used for corn borer, not cotton.
Mainly lepidopteran insect pests, especially cotton bollworms. Bt toxins are insect-group specific and do not affect nematodes or fungi.
Bt cotton makes a toxin protein that kills insects that eat it. RNAi crops silence a specific gene in a pest (for example a nematode) so the pest cannot survive. Bt = insect resistance; RNAi = nematode resistance.
