Class 12 Biology

Applications of Biotechnology

NCERT Exercise

Question 1: Crystals of Bt toxin produced by some bacteria do not kill the bacteria themselves because

(a) Bacteria are resistant to the toxin
(b) Toxin is immature
(c) Toxin is inactive
(d) Bacteria encloses toxin in a special sac

Answer: (c) Toxin is inactive

Question 2: What are transgenic bacteria? Illustrate using any one example.

Answer: Genetically modified bacteria are called transgenic bacteria. Transgenic bacteria are utilized to produce various products beneficial for human beings. For example; E. coli is genetically modified to produce human insulin.

Question 3: Compare and contrast the advantages and disadvantages of production of genetically modified crops.

Answer: Following are the advantages of genetically modified crops:

Disadvantages of genetically modified crops:

Introduction of a transgenic plant into ecosystem may result in unseen and potentially harmful consequences. Some introduced genes may harm beneficial organisms, and even harm human beings. Many organizations have been protesting against the use of GM crops.

Question 4: What are Cry proteins? Name an organism that produces it. How has man exploited this protein to his benefit?

Answer: The toxins produced by B. thuringiensis are called Cry proteins or Cry toxins. Different Cry proteins are effective against different insect pests. Based on this property, different varieties of GM crops have been produced to benefit the mankind.

Question 5: What is gene therapy? Illustrate using the example of adenosine deaminase (ADA) deficiency.

Answer: Gene therapy is a collection of methods that allows correction of a gene defect that has been diagnosed in a child/embryo. Correction of a genetic defect involves delivery of a normal gene into the individual or embryo. The normal gene takes over the function of and compensates for the non-functional gene.

ADA deficiency is caused due to the deletion of the gene for ADA. This enzyme is crucial for proper functioning of the immune system. Conventional treatment of ADA deficiency do not ensure complete cure.

The first step towards gene therapy involves taking lymphocytes from the blood of the patient and growing them in a culture. Then a functional ADA cDNA (using a retroviral vector) is introduced into these lymphocytes. The lymphocytes are then returned to the patient’s body. Since lymphocytes die after some time, the patient needs periodic infusion of genetically modified lymphocytes. But if the gene isolate from marrow cells producing ADA is introduced into cells at early embryonic stages, it could be a permanent cure.

Question 6: Digrammatically represent the experimental steps in cloning and expressing a human gene (say the gene for growth hormone) into a bacterium like E. coli?


steps of recombinant DNA technology

Image Ref: Wikipedia

Question 7: Can you suggest a method to remove oil (hydrocarbon) from seeds based on your understanding of rDNA technology and chemistry of oil?

Answer: The oil in seed is composed of glycerol or fatty acids. Production of these molecules is governed by particular genes. Such genes can be removed by using rDNA technology. This will help in production of oil-less seeds.

Question 8: Find out from internet what is golden rice?

Answer: A recombinant variety of rice that has been engineered to express the enzymes responsible for β-carotene biosynthesis is called golden rice. This variety of rice has the potential for reducing vitamin A deficiency. This has yet to get regulatory permission and hence is not in use at present.

Question 9: Does our blood have proteases and nucleases?

Answer: Our blood does not contain the enzymes proteases and nucleases.

Question 10: Consult internet and find out how to make orally active protein pharmaceutical. What is the major problem to be encountered?

Answer: Protein poses the challenge of poor bioavailability when given orally. This happens because of enzymatic degradation, poor membrane permeability and large molecular size of protein. Various methods have been tried to make orally active protein pharmaceutical but little success has been achieved in this regard. So, effective orally active pharmaceutical are not available till date.