Biotechnology and its ApplicationsClass 12 Biology NCERT Solutions

The meristem (apical and axillary) is the best part of the plant for making virus-free plants. This is because the meristematic tissue is a region of actively dividing cells and has a high metabolic rate, which is believed to interfere with virus multiplication. Consequently, even if the rest of the plant is infected with a virus, the meristem often remains virus-free. By excising the meristem and growing it in vitro through tissue culture, a whole, healthy, and virus-free plant can be regenerated.

The major advantage of producing plants by micropropagation (tissue culture) is the ability to produce a very large number of plants from a single parent plant in a very short duration. All the plants produced through this method are genetically identical to the original plant from which they were grown, and are known as somaclones. This ensures the propagation and preservation of desirable traits, such as high yield or disease resistance, uniformly across a large population of plants.

The nutrient medium used for the in vitro propagation of an explant is a sterile, gel-based medium containing various components essential for plant growth. These components are:

The correct answer is (c) toxin is inactive.

Explanation: The Bt toxin is produced by the bacterium Bacillus thuringiensis in an inactive form called a protoxin. This protoxin only becomes active under the specific alkaline pH conditions found in the midgut of certain insects. Since the internal environment of the bacterium is not alkaline, the toxin remains in its inactive state and is therefore harmless to the bacterium itself.

Transgenic bacteria are bacteria whose genetic material has been altered by the introduction and expression of a foreign gene from another organism using recombinant DNA technology. These are a type of Genetically Modified Organism (GMO).

Example: Production of Human Insulin A prominent example is the use of the bacterium Escherichia coli (E. coli) to produce human insulin.

Cry Proteins: Cry proteins are a class of toxic, insecticidal crystal proteins. They are produced in an inactive form (protoxin) and become active only in the alkaline gut of certain insects.

Organism: The organism that produces Cry proteins is the soil bacterium Bacillus thuringiensis (Bt).

Exploitation by Humans: Humans have exploited this protein for agricultural benefit by creating pest-resistant genetically modified (GM) crops. The process is as follows:

Gene Therapy: Gene therapy is a collection of methods aimed at correcting a genetic defect to treat a disease. It typically involves inserting a normal, functional gene into an individual's cells to compensate for a non-functional or missing gene.

Illustration with Adenosine Deaminase (ADA) Deficiency: ADA deficiency is a severe immunodeficiency disorder caused by the deletion or mutation of the gene that codes for the enzyme adenosine deaminase. This enzyme is essential for the functioning of the immune system.

Gene therapy for ADA deficiency involves the following steps:

This method is not a permanent cure because lymphocytes are not immortal and have a limited lifespan. Therefore, the patient requires periodic infusions of the modified cells. A permanent cure could potentially be achieved if the gene is introduced into hematopoietic stem cells from the bone marrow at an early embryonic stage.

While a diagram cannot be drawn here, the experimental steps for cloning and expressing the human growth hormone gene in E. coli are as follows. A diagram would visually represent this process:

Yes, a method based on recombinant DNA (rDNA) technology, specifically RNA interference (RNAi), can be used to create seeds with reduced or no oil content. Oil synthesis in seeds is a metabolic pathway controlled by specific enzymes, which are encoded by genes.

The method would involve these steps:

Golden Rice is a variety of rice (Oryza sativa) that has been genetically engineered to biosynthesize beta-carotene, a precursor of Vitamin A, in the edible part of the grain. Normal rice does not produce beta-carotene, which is why its grains are white. The presence of beta-carotene gives Golden Rice its characteristic yellow-orange color.

The primary goal for developing Golden Rice is to address Vitamin A deficiency, a significant public health issue in many parts of the developing world where rice is a staple food. Vitamin A deficiency can lead to severe health problems, including blindness in children and a weakened immune system. By providing a source of Vitamin A in a commonly consumed food, Golden Rice is intended to be a cost-effective and sustainable way to improve nutrition and health in these populations.

Yes, our blood does contain both proteases and nucleases, but their activity is tightly regulated to prevent damage to the body's own tissues and essential molecules.

Making a protein-based pharmaceutical (like insulin or growth hormone) orally active is a major challenge in drug development. Several strategies are being researched to achieve this:

The Major Problem to be Encountered: The primary obstacle to the oral administration of protein drugs is their degradation in the gastrointestinal (GI) tract and their poor absorption into the bloodstream.