Question

Bt- cotton is resistant for-
A. Round-worm
B. Fluke-worm
C. Boll-worm
D. Pin-worm

Answer 1

Bt stands for Bacillus thuringiensis that is a gram-positive bacteria. It is a soil-dwelling bacteria that produces a natural toxin that is fatal to certain herbivorous insects. It is safe for humans and thus is used as a biopesticide which is environmentally compatible.

Complete answer:
Due to the presence of insecticidal properties, Bt (a protein family originated from the strains of Bacillus thuringiensis ), are incorporated into major crops which in turn provides them insect resistance. Cotton has a very high economic value and it is highly affected by many insect pests. To provide insect resistance, a genetically modified crop variety.
Bt Cotton was introduced which was resistant to many pests. These crops are genetically modified by the addition of genes that encode toxin crystals in the Cry group of endotoxin. This toxin crystal when ingested by certain insect populations would dissolve their gut lining leading to their death. This was found to be effective mostly against the cotton bollworm insect.
Transgenic Bt cotton has played an important part in the Integrated pest management as it saved the cotton crops from the lepidopterous larvae.

Hence, the correct answer is option (C)

Note: The Cry molecules get activated by the high pH of the digestive tract of the insect, after activation these molecules bind to the cadherin-like proteins forming a cry ion channel which affects the efflux of potassium ions leading to an internal infection in the gut.