The VIDYANKER team has thoughtfully prepared the NCERT Solutions for Class 12 Biology Chapter 12, "Biotechnology and its Applications" These solutions are designed to help you tackle the NCERT textbook questions with ease. We recommend going through the chapter's theory before diving into the solutions for a deeper understanding. Feel free to share these NCERT Solutions for Class 12 Biology with others—learning is always better when shared!
QUESTIONS FROM TEXTBOOK SOLVED
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.
Ans: The correct answer is (c) toxin is inactive.
In reality, the crystals of Bt toxin produced by Bacillus thuringiensis bacteria are in fact, in an inactive form called protoxin. The toxin does not harm the bacteria since it is protoxin that comes alive only after ingestion by an insect with its gut being alkaline, where the protoxin gets converted into its active form that kills the insect by damaging the lining of its gut.
2. What are transgenic bacteria? Illustrate using any one example.
Ans: Transgenic bacteria: These are bacteria that have carrying gene or genes generally coming from an unrelated organism in their genome. For example, if the human insulin gene is inserted into the isolated plasmid of the E.coli bacterium and the recombinant DNA is transfected into a new bacterium then that is said to be transgenic or transformed bacterium.
3. Compare and contrast the advantages and disadvantages of production of genetically modified crops.
Ans: The production of genetically modified (GM) or transgenic plants has many advantages.
- Most of the genetically modified crops have been developed for pest resistance, which increases crop productivity and reduces reliance on chemical pesticides.
- There are many varieties of genetically modified food crops having good nutritional quality. For instance, the golden rice is a transgenic variety in rice which is rich with vitamin A.
- These plants do not let the loss of fertility of the soil increase with an increase in the efficiency of mineral usage.
- They are highly resistant to unfavourable abiotic conditions.
- The use of genitically modified crops decreases the post-harvesting loss of crops.
But, however, the use of genetically modified crops across the globe has several controversies. The crop would definitely have an effect on the native biodiversity in that region. For instance, applying Bt toxin to reduce the amount of pesticides employed has proved to be harmful for the beneficial pollinators like honey bee. If the gene expressed for Bt toxin gets expressed in the pollen, then the honey bee might be affected. Consequently, the process of pollination by honey bees would be affected. Moreover, genetic modifications are also affecting human health. They provide allergens and certain antibiotic resistance markers in the body. In addition, they can produce genetic pollution in the wild relatives of the crop plants. It results in affecting our natural environment.
4. What are Cry proteins? Name an organism that produces it. How has man exploited this protein to his benefit?
Ans: The cry genes encode for cry proteins. These are toxins produced by Bacillus thuringiensis bacteria. These proteins are carried within the bacterium in an inactive form. When the inactive toxin protein is consumed by the insect, it is activated by the alkaline pH of the gut. This eventually leads to the lysis of the epithelial cell and results in the death of the insect. Thus, man has made use of this protein to create some of the transgenic crops with insect-resistant properties like Bt cotton, Bt corn etc.
5. What is gene therapy? Illustrate using the example of adenosine deaminase (ADA) deficiency.
Ans: Gene therapy is defined as the correction of malfunctioning or deficient gen by repairing or adding a correct copy. ADA is an extremely rare genetic disorder because of the deletion of the gene responsible for adenosine deaminase. The enzyme is vital for the functioning of the immune system. It can be treated by gene therapy. This gene is transfected into early embryonic cells of the bone marrow for permanent use.
6. Digrammatically represent the experimental steps in cloning and expressing an human gene (say the gene for growth hormone) into a bacterium like E. coli?
Ans: 
7. Can you suggest a method to remove oil (hydrocarbon) from seeds based on your understanding of rDNA technology and chemistry of oil?
Ans: Recombinant DNA technology, shortened to rDNA, is a technique of genetic material manipulation in an organism for an intended purpose.
For instance, such a technology can be used to remove oil from seeds. The costituentsf oil are glycerol and fatty acids. Using rDNA, one can obtain oilless seeds by stoping the synthesis of either glycerol or fatty acids. This is done by removing the specific gene responsible for the synthesis.
8. Find out from internet what is golden rice.
Ans: Golden rice is a genetically modified version of the species Oryza sativa. This type of rice is developed as an enriched food product in regions where the diet does not provide enough dietary vitamin A. The genetically engineered rice variety consists of a precursor for pro-vitamin A called beta-carotene. Beta-carotene is a pigment created in the leaf blades of the rice plant. However, it does not appear in the endosperm of the seed. This is because beta-carotene pigment assists in photosynthesis while photosynthesis does not take place in endosperm. Since beta-carotene is a precursor of pro-vitamin A, it is added to the rice variety to satisfy the deficit in dietary vitamin A. This is simple and an inexpensive substitute to vitamin supplements. However, this strain of rice has also encountered a great resistance from environmentalists. Hence, they have yet to be accessed in the market for human consumption.
9. Does our blood have proteases and nucleases?
Ans: No, the blood of human beings does not have the enzymes, nucleases and proteases. Blood serum in human beings contains all sorts of protease inhibitors that protect the blood proteins from getting degraded by the action of proteases. The enzyme, nucleases catalyzes the hydrolysis of nucleic acids that is absent in blood.
10. Consult internet and find out how to make orally activ&protein pharmaceutical. What is the major problem to be encountered?
Ans: Orally active protein product that is successfully manufactured is vaccines for preventions of infectious diseases such as hepatitis B, herpes, influenza, etc. Gene for antigen are isolated from bacteria and grown along with cut leaf portions of potato plant in antibiotic medium – followed by callus formation and recombinant/transgenic potato are obtained which contain those vaccines.
