CBSE Class 12 Biotechnology Worksheet Set A

Short Answer Type Questions

Question. Taking examples under each category, discuss upstream and downstream processing.
Answer : The fermentation process is the basis of many industries in order to produce diverse products. Fermentation means a process in which microorganisms that are cultured on a large scale, convert a substrate into a product which is useful to human. The fermentation process is divided into two stages namely Upstream and downstream processing both of these processes can be discussed taking an example of citric acid production. The upstream processing in biotechnology involves identifying a material. This forms the initial process of fermentation. It deals with inoculum preparation, preparation of culture media, scale up of the entire process and inoculation. When the products are subjected to a series of processes including separation and purification of the product, it is collectively known as downstream processing. It deals with the post-harvest product, i.e., recovery-clarification, purification, polishing and formulation till the packaging of the desired product.

Question. When a foreign DNA is introduced into an organism, how is it maintained in the host and how is it transferred to the progeny of the organism?
Answer : Foreign gene is usually ligated to a plasmid vector and introduced in the host. As plasmid replicates, and makes multiple copies of itself, so does the foreign gene gets replicated and its several copies are made. When the host organism divides, its progeny also receives the plasmid. DNA containing the foreign gene. The whole process can be visualised in the figure given below  (Image 220)

Question. Bt cotton is resistant to pest, such as lepidopteran, dipterans and coleopterans Is Bt cotton also resistant to other pests as well?
Answer : Bt cotton is made resistant to certain specific taxa of pests (lepidopteran, dipterans and coleopterans). It is quite likely that in future, some other pests may infest these Bt-cotton plants. It is similar to immunisation against smallpox which does not provide immunity against other pathogens like those, that causes cholera, typhoid etc.

Question. Define antigen and antibody. Name any two diagnostic kits based upon them.
Answer : An antigen is a foreign substance that elicits the immune response and results in the forma.tion of an antibody. Antibody is a protein that is synthesised by the body in response to an antigen. Antigen and antibody shows high degree of specificity in binding to each other. Two diagnostic kits based on antigen-antibody interaction are (a) ELISA for HIV. (b) Pregnancy test kits.

Question. ELISA technique is based on the principles of antigen-antibody interaction. Can this technique be used in the molecular diagnosis of a genetic disorder, such as phenylketonuria?
Answer : Yes, one can use antibody against the enzyme (that is responsible for the metabolism of phenylanaline) to develop ELISA based diagnostic technique. The patient, in which the enzyme-protein complex is absent would give a negative result in ELISA when compared to the normal individual.

Question. How is a mature, functional insulin hormone different from its pro-hormone form?
Answer : Mature functional insulin is obtained by the processing of pro-hormone which contains an extra peptide called C-peptide or connecting peptide. It connects the A and B chains in proinsulin. This C-peptide is removed during the maturation of pro-insulin to insulin and A and B chains gets linked by disulphide linkage.

Question. Gene therapy is an attempt to correct a genetic defect by providing a normal gene into the individual. By this the normal function can be restored. An alternate method would be to provide the gene product (protein/enzyme) known as enzyme replacement therapy, which would also restore the function. Which in your opinion is a better option? Give reason for your answer.
Answer : Gene therapy would be a better option because it has the potential to completely cure the patient. It is because the correct gene once introduced in the patient, can continue to produce the correct protein enzyme. Enzyme therapy does not offer permanent cure as it needs to be given to the patient on regular basis. It is also more expensive.

Question. Transgenic animals are the animals in which a foreign gene is expressed. Such animals can be used to study the fundamental biological process, phenomenon as well as for producing products useful for mankind. Give one example for each type.
Answer : Transgenic animals are the animals in which a foreign genes are expressed. Such animals can be used to study the fundamental biological process/phenomenon, e.g., by using model organisms like mouse we can determine how genes are regulated (gene regulation), how they affect the normal functions of the body and its development, etc. Transgenic animals are also used for producing products useful for mankind, e.g., Transgenic cow (rosie). Which produced human protein enriched milk (2.4 g/L). The milk contained the human alpha-lactalbumin and was nutritionally a more balanced product for human babies than natural cow-milk.

Long Answer Type Questions

Question. What are the various advantages of using genetically modified plants to increase the overall yield of the crop?
Answer : Genetically modified plants have been useful in many ways as follows (i) These plants are more tolerant to abiotic stresses (cold, drought, salt, heat). (ii) They have reduced the reliance on chemical pesticides (pest-resistant crops). (iii) They helped to reduce post harvest losses. (iv) They increases the efficiency of mineral usage by plants (this prevents early exhaustion of fertility of soil). (v) Enhanced nutritional value of food, e.g., vitamin-A enriched rice. In addition to these uses, GM plants have been used to create tailor-made plants to supply alternative resources to industries, in the form of starches, fuels and pharmaceuticals.

Question. Explain with the help of one example how genetically modified plants can (a) Reduce usage of chemical pesticides. (b) Enhance nutritional value of food crops.
Answer : (a) Genetically modified plants can reduce the usage of chemical pesticides by introducing pest resistant plants. e.g., There are several nematodes that parasitie, a wide variety of plants and animals including human beings. A nematode Meloidogyne incognita infects the roots of tobacco plants and causes a great reduction in yield. A novel strategy was adopted to prevent this infestation which was based on the process of RNA interference (RNAi). Using Agrobacterium vectors, nematode-specific genes were introduced into the host plant. The introduction of DNA was such that it produced both sense and antisense RNA in the host cells. These two RNA’s being complementary to each other formed a double stranded RNA that initiated RNAi and thus, silenced the specific mRNA of the nematode. The consequence was that the parasite could not survive in a transgenic host expressing specific interfering RNA. (b) Genetically modified plants can enhance nutritional value of food crops. e.g., ‘Golden rice’ developed at Swiss Federal Institute of technology is an example of nutritionally modified crop. It is rich in vitamin-A (b-carotene). The rice grains are golden-yellow in colour. It contains ‘beta-carotene’ gene from daffodil plant and also from some bacteria. Golden rice can prevent child blindness which is caused due to the deficiency of vitamin-A.

Question. A patient is suffering from ADA deficiency. Can he be cured? How? K Thinking Process A patient suffering from ADA deficiency can be cured by using ‘gene therapy’. Gene therapy is a collection of methods that allows the correction of a gene defect that has been diagnosed in a child/embryo.
Answer : ADA enzyme is crucial for the immune system to function. Deletion of the gene for adenosine deaminase results into ADA deficiency. In some children, ADA deficiency can be cured by bone-marrow transplantation, while in others it can be treated by enzyme replacement therapy, in which functional ADA is given to the patient by injection. But the problem with both of these approaches is that they are not completely curative. It may recurrent in nature as in the process of gene therapy, lymphocytes used are found not to be immortal in nature and the patient requires a periodic infusion of such genetically engineered lymphocytes. For permanent cure, gene isolated from the bone-marrow cells producing ADA is introduced into cells at early embryonic stages.

Question. List the disadvantages of insulin obtained from the pancreas of slaughtered cows and pigs.
Answer : The disadvantages of insulin obtained from the pancreas of slaughtered cows and pigs are (i) Insulin being a hormone is produced in very little amounts in the body. Hence, a large number of animals need to be sacrificed for obtaining small quantities of insulin. This makes the cost of insulin very high (Demand being many fold higher than supply). (ii) Slaughtering of animals is not ethical. (iii) There is a potential of immune response in humans against the administered insulin which is derived from animals. (iv) There is possibility of slaughtered animals being infested with some infectious microorganism which may contaminate insulin.

Question. List the advantages of recombinant insulin.
Answer : The advantages of recombinant insulin are (i) There is no need of animals to be sacrificed for the production of recombinant insulin. (ii) Recombinant insulin was not found allergic to patients, while the insulin from an animal source caused some patients to develop allergy or other types of reactions to the foreign protein. (iii) The cost of recombinant insulin is not very high. (Supply being many fold higher than demand)

1. Identify the following: 
i. 5’-GAATTC-3’
3’-CTTAAG-5’
ii. 5’G AATTC-3’
3’-CTTAA G-5’

2. How can very low concentration of bacteria or virus be detected? 

3. How is the action of exonuclease different from that of endonuclease? 

4. Expand GEAC. What is its role in Biotechnology? 

5. Name the organism from which Ti plasmid is isolated. Explain the use of this plasmid in biotechnology. 

6. A recombinant DNA is formed when sticky ends of vector DNA and foreign DNA join. Explain how the sticky ends are formed and get joined.

7. How infestation of Meoidegyne incognitia was prevented in tobacco plant?

8. i) Mention the number of primers required in each cycle of polymerase chain Reaction (PCR). Write the role of primers and DNA polymerase in PCR.
(ii) Give the characteristic feature and source organism of the DNA polymerase used in PCR. 

9. What is Ti plasmid? Name the organism where it is found. How does it help in genetic engineering?

10. How does a transgenic organism different from the rest of its population? Give any two examples of such organism for human advantage.

11. How did Eli lilly synthesize the human insulin? Mention difference between this insulin and the one produced by the human pancreas.

12. What is ADA deficiency? Describe three methods to cure it?

13. What is the advantage of recombinant therapeutics over similar products isolated from non-human sources? Name any two recombinant products used as medicine. 3

14. With an example, explain how Biotechnology has been applied in raising pest resistant plants by RNA interference?

15. Why is Agrobacterium mediated genetic transformation described as natural genetic engineering in plants?

16. What is PCR? Describe the process of PCR.

17. What is the advantage of modern genetic techniques over traditional hybridization method?

18. What is cloning vector? Explain the technique of using such a vector in E. coli.

19. What are transgenic bacteria? Illustrate using one example.

20. Write a brief account of genetically engineered insulin.

21. (i) Name the organism in which the vector shown is inserted to get the copies of the desired gene. (ii) Mention the area labeled in the vector responsible for controlling the copy Number of the inserted gene. (iii) Name and explain the role of a selectable marker in the vector shown.

22. Name the insect pest that is killed by the products of cryIAC gene. Explain how the gene makes the plant resistant to the insect pest.

23. Represent diagrammatically the steps in amplification of a DNA segment. Who designed this process?

24. Represent diagrammatically the steps in involved in rDNA technology.

25. Name the soil bacterium that produces a protein/chemical that is toxic to insect pests. Show with example that the different forms of them encoded by different forms of the genes are insect specific.