Biotechnology and its Applications

The meristematic region is best suited because it is generally free of virus. Even if the plant is infected, the virus usually does not enter the meristem, so by removing the meristem and growing it *in vitro*, one can obtain virus-free plants.

The major advantage of micropropagation is that it allows the production of thousands of plants very quickly. These plants are genetically identical to the original plant, so good varieties can be multiplied fast on a commercial scale.

The nutrient medium for *in vitro* propagation must supply: a carbon source such as sucrose, inorganic salts, vitamins, amino acids, and growth regulators like auxins and cytokinins.

Bt toxin in the bacterium is present as an inactive protoxin. It becomes active only after being ingested by an insect, where the alkaline gut converts it into the active toxin. Therefore, the bacteria themselves are not killed by it.

Transgenic bacteria are bacteria whose genome has been modified by introducing an extra foreign gene so that they can express a desired product. For example, E. coli has been genetically engineered with the genes for the A and B chains of human insulin; the chains are produced separately and then combined to form human insulin.

Advantages of genetically modified crops:
- They can be made tolerant to abiotic stresses like cold, drought, salt and heat.
- They reduce dependence on chemical pesticides because pest-resistant varieties can be made.
- They help in reducing post-harvest losses.
- They can show better mineral use efficiency, preventing early exhaustion of soil fertility.
- They can have enhanced nutritional value, for example golden rice enriched with vitamin A.
- They can be tailored to provide starches, fuels and pharmaceuticals for industry.

Disadvantages / concerns:
- They may have unpredictable effects when introduced into the ecosystem.
- Their use raises ethical issues and concerns about safety.
- There are concerns related to patents and biopiracy, where companies may exploit biological resources and traditional knowledge without proper permission or compensation.

Cry proteins are insecticidal proteins produced by the bacterium Bacillus thuringiensis (Bt). Different cry genes produce toxins effective against specific insect groups. Humans have exploited this by cloning cry genes into crop plants to make Bt crops such as Bt cotton, Bt corn, etc., which are resistant to insect pests and reduce the need for insecticides.