CBSE Class 12 Biology Biotechnology and its Applications Assignment Set B

Case-based MCQs

Attempt any four sub-parts from each question.

I. Read the following text and answer questions from given below :
Plants having foreign genes in their genome through genetic engineering are called transgenic plants. Genes can be incorporated either through a vector or through direct introduction of DNA. Bt cotton is a genetically modified organism which is pest resistant. It contains gene cry I Ac and cry II Ab of Bacillus thuringiensis. It is used to control lepidopterans, coleopterans and dipterans. Bt cotton can resist cotton bollworm and produce higher yields. Cry gene produces cry protein or Bt toxin. It is an endotoxin which remains as protoxin in plants and converted to active toxin after getting ingested by the insects. Alkaline pH of the insect gut solubilizes the protein crystals, the activated toxin creates pores to the mid gut wall of the insects
which cause them to death. 

Question. Cotton bollworms are killed by the protein encoded by the gene
(A) cry I Ac
(B) cry I Ab
(C) cry II Ab
(D) both A and C
Answer : D

Question. Bacillus thuringiensis is a
(A) air borne bacteria
(B) soil borne fungus
(C) soil borne bacteria
(D) food borne bacteria
Answer : C

Question. Identify which of the following is not an advantage of GM crops?
(A) GM plants enhance nutritional value of food.
(B) GM plants are more tolerant to abiotic stresses.
(C) GM plants have helped to reduce post-harvest losses.
(D) GM plants can cause gene transfer to non-target plant species.
Answer : D

Question. Some strains of Bacillus thuringiensis can kill certain insects such as _______
(A) lepidopterans
(B) scorpion
(C) fruit fly
(D) dragonfly
Answer : A

Question. What is true about Bt cotton crops?
(A) They are fungal resistant
(B) They are insect resistant
(C) They are drought resistant
(D) All of these
Answer : D

II. Read the following text and answer questions from given below :

Biotechnology can be defined as the use of biological processes in industry and technology.
During the past three decades biotechnology has gained attention due to the gene cloning process.
Biotechnological applications are playing important role in agriculture. They are used in agro-chemical based agriculture, in organic farming, genetically engineered crop-based agriculture. The green revolution is the milestone or result of these biotechnological processes.

Question. What does ‘Bt’ in BT toxin represent ?
(A) Bioterrorism
(B) Blue tooth toxin
(C) Bleeding toxin
(D) Bacillus thuringiensis
Answer : D

Question. ___________ has been called the “Father of Green Revolution.“
(A) Dr. Verghese Kurien
(B) Norman E. Borlaug
(C) Sam Pitroda
(D) Dr. Arun Krishnan
Answer : B

Question. The main objective of biotechnology in agriculture is :
(A) To increase the plant weight
(B) To reduce pre-harvest losses.
(C) To produce pest resistant varieties of plants
(D) To increase the production of seeds
Answer : C

Question. Which among the following may be considered as an application of biotechnology ?
(A) Energy production
(B) Waste treatment
(C) Bioremediation
(D) All of these.
Answer : D

Directions : In the following questions a statement of assertion (A) is followed by a statement of reason
(R). Mark the correct choice as :
(A) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).
(B) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).
(C) Assertion (A) is true but reason (R) is false.
(D) Assertion (A) is false but reason (R) is true.

Question. Assertion (A) : Bt toxin crystals contain insecticidal protein.
Reason (R) : B. thruingiensis forms these protein crystals continuously during their growth period.
Answer : C 

Very Short Answer Type Questions

Question. What are stem cells ?
Answer : Stem cells are undifferentiated or “blank” cells. This means they are capable of developing into cells that serve numerous functions in different parts of the body.

Question. What are Cry genes ? In which organism are they present ?
Answer : The genes which code for Bt toxin / Cry proteins (toxic proteins), Bacillus thuringiensis.

Question. Mention the chemical change that proinsulin undergoes, to be able to act as mature insulin. 
Answer : Removal of C-peptide (from pro-insulin).

Question. List the type of cry genes that provide resistance to corn plants and cotton plants respectively against lepidopterans
Answer : cryIAc / cryIIAb - cotton. 
cryIAb - corn.

Question. What is biopiracy ?
Answer : Illegal / non authorized / non compensated use of bioresources by organisations.

Question. Bt-toxins are released as inactive crystals in the bacterial body. What happens to it in the cotton bollworm body that it kills the bollworm. 
Answer : It is converted into an active protein (due to alkaline pH of the gut of the bollworm). The toxin binds to midgut cells / create pores / causes cell swelling and lysis that kills the bollworm.

Question. Suggest a molecular diagnostic procedure that detects HIV in suspected AIDS patients.
Answer : PCR and ELISA. 

Question. Write the use of stem cells.
Answer : Stem cells can be used to grow new cells in a laboratory to replace damaged organs or tissues.

Question. What are transgenic animals. Give an example. 
Answer : Animals whose DNA is manipulated to possess and express an extra (foreign) gene e.g., Rosie - transgenic cow.

Short Answer Type Questions

Question. Explain the events that occur in the host cell on introduction of nematode-resistant gene into the tobacco plant by using Agrobacterium vectors. 
Answer : l RNA interference
• Silencing of a specific mRNA due to a complementary RNA
• dsRNA/Introduction of DNA was such that it produced both sense/ and anti-sense RNA in the host cells/these two RNAs formed dsRNA that initiated RNAi. 

Question. A corn farmer has a perennial problem of corn-borer infestation in his crop. Being environmental conscious he does not want to spray insecticides. Suggest solution based on your knowledge of biotechnology. Write the steps to be carried out to achieve it.
Answer : Isolation of Bt toxin gene from Bacillus thuringiensis, incorporated into corn, toxin coded by gene cry IAb in corn, kills the pests/pest dies.

Question. What are the objectives of GEAC ?
                         OR
Mention two objectives of setting up GEAC by our government.
Answer : Objectives of GEAC :
(i) To examine the validity of GMO i.e., genetic modification of organisms research.
(ii) Safety of introducing GMOs for public use.

Question. Explain how Eli Lilly an American company produced insulin by recombinant DNA technology.
                                                 OR
Explain how the company Eli Lilly was able to produce human insulin using rDNA technique.
                                                                   OR
Recombinant DNA-technology is of great importance in the field of medicine. With the help of a flow chart, show how this technology has been used in preparing genetically engineered human insulins.
Answer : In 1983, Eli Lily and American company prepared two DNA sequences corresponding to A and B chains of human insulin, introduced them in plasmids of E. coli to produce insulin chains. Chains A and B were produced separately, extracted and combined by creating disulfide bonds to form human insulin.

Question. State the initiative taken by the Indian Parliament towards biopiracy ?
Answer : Indian Parliament has passed the second amendment of the Patent Bill, which deals with patent terms, emergency provisions and research and development initiatives. 

Question. Why do lepidopterans die when they feed on Bt cotton plant ? Explain how does it happen.
Answer : Bt cotton contains inactive toxin protein / protoxin / insecticidal protein / crystal protein, once the insects ingest it, the inactive protoxins are converted into active form due to alkaline pH in gut, which solubilises the crystals, activated toxins binds to surface of midgut (epithelial cells), create pores, causes cell swelling, lysis eventually leading the death of the insect pest. 

Question. Explain the various steps involved in the production of artificial insulin.
Answer : Two DNA sequences corresponding to A and B polypeptide chains of human insulin were prepared, these were introduced into E. coli to produce A and B chains separately, these chains were extracted and combined by creating disulphide bonds.

Question. Explain the application of biotechnology in producing Bt cotton.
Answer : Bt toxin gene has been cloned from the bacteria, and has been expressed in plants, to provide resistance to insects (without the need for synthetic insecticide). Bt toxin gene forms protein crystals.
These crystals contain a toxic insecticidal protein. Bt toxin protein exists as inactive protoxin in the host, but once the insect ingests the inactive toxin, it is converted into active form of toxin, due to alkaline pH of the gut which solubilises the crystals, causing death of the insect. 

Question. Specific Bt toxin genes isolated from Bacillus thuringiensis incorporated into cotton is coded by the genes cryIAc and cryIIAb that control the cotton bollworms. Mention its mode of action. 
Answer : (i) Bacillus forms protein crystals that contain a toxic insecticidal protein.
(ii) Once an insect ingests the inactive toxin, it is converted into an active form.
(ii) The toxin in the form of crystals gets solubilised due to alkaline pH in the gut.
(iv) The activated toxin binds to the surface of gut epithelial cells and perforate the walls causing the death of insect larva. 

Question. Name the organism from which the ‘cry‘ genes are isolated. Mention with the help of suitable example why and how biotechnologists have made use of ‘cry‘ genes ?
Answer : Bacillus thuringiensis 
(i) Source of insecticidal (crystal) protein that controls the cotton bollworms / corn borer. 
(ii) Specific Bt toxin genes were isolated from Bacillus thuringiensis, incorporated into several crop plants such as cotton. 

Question. The Indian Government refuted the attempt by a multinational company (MNC) to patent the antiseptic property of curcumin derived from Turmeric. Analyze the unethical practice adopted by the MNC, state its implications and suggest provisions in the Indian Law to prevent such malpractices.
Answer : (i) MNC wanted to encash on our rich legacy by biopiracy.
(ii) It leads to injustice, inadequate compensation and unauthorized exploitation of traditional knowledge of the country.
(iii) Second amendment of the Indian Patents Bill takes into consideration issues related to patent terms, emergency provisions, and research and development initiative.

Question. Explain the application of rDNA technology to produce insulin.
Answer : Human insulin is synthesised as a pro-hormone. The pro-hormone contains an extra C-peptide. The C-peptide is not present in mature insulin and is removed during maturation. Eli-Lilly American company prepared two DNA sequences, corresponding to A and B chains of human insulin and introduced them in plasmids of E. coli to produce insulin chains. Chain A and B were produced separately, extracted and combined by creating disulphide bonds to form human insulin.

Question. What was the challenge for production of insulin using rDNA techniques ? How did Eli Lilly produce insulin using rDNA technology?
Answer : The challenge for production of insulin using rDNA technique was getting insulin assembled into a mature form. 1
(i) Prepared two DNA sequence corresponding to A and B chains of human insulin.
(ii) Introduced them in plasmids of E. coli to produce insulin chains.
(iii) Chains A and B were produced separately.
(iv) Extracted and combined by creating disulfide bonds to form human insulin 

Question. (a) What are transgenic animals ?
(b) Name the transgenic animal having the largest number amongst all the existing transgenic animals.
(c) Mention any three purposes for which these animals are produced.
Answer : (a) Animals that have had their DNA manipulated to possess and express an extra / foreign gene. 1
(b) Mice.
(c) (i) Normal physiology and development.
(ii) Study of disease.
(iii) Biological products.
(iv) Vaccine safety.
(v) Chemical safety testing. 

Question. What is GMO ? List any five possible advantages of a GMO to a farmer.
                                                         OR
People are quite apprehensive to use GM crops. Give three arguments in support of GM crops so as to convince the people in favour of such crops.
Answer : Plants / bacteria / fungi / animals whose genes have been altered by manipulation. 
Tolerance to abiotic stresses / like cold / drought / salt / heat, reduced reliance on chemical pesticides / pest resistant crops, reduce post-harvest losses, increased efficiency of mineral usage by plants, enhanced nutritional value to create tailor-made plant. 

Question. (a) While cloning vectors, which of the two will be preferred by biotechnologists - bacteriophages or plasmids. Justify with reason.
(b) Name the first transgenic cow developed and state the improvement in the quality of the product produced by it.
Answer : (a) Bacteriophages, because they have very high copy numbers of their genome within the bacterial cells whereas some plasmids may have only one or two copies per cell and others may have 15-100 copies per cell. 1
(b) Rosie, it produced human protein-enriched milk (2.4 gm per litre). 

Question. List any four ways by which GMO’s have been useful for enhanced crop output.
Answer : Make crops more tolerant to abiotic / cold / heat / drought / salt stresses / Reduces reliance on chemical pesticides (pest-resistant crops) / Reduce post harvest losses / Increased efficiency of mineral usage by plant (prevents early exhaustion of soil fertility) / Enhanced nutritional value of food (example vitamin A enriched rice / starch) / To create tailor-made plants for non food purposes (to supply alternative resources of fuels / pharmaceuticals to industries).

Long Answer Type Questions

Question. Explain the role of Agrobacterium tumefaciens in developing resistance in tobacco plant against nematode Meloidegyne incognitia. Name the processes responsible for this.
Answer : Agrobacterium tumefaciens is capable of transforming a piece of their own genome termed as T-DNA into the infected plant cells to create the desired GMO. A nematode Meloidegyne incognitia infects the roots of tobacco plants and causes a great reduction in yield. RNA interference (RNAi) strategy is used to prevent this infestation.
RNAi is a method of cellular defence in all eukaryotic organisms. It is a process by which double-stranded RNA (dsRNA) directs sequence-specific degradation of mRNA. It prevents the translation of a specific mRNA (silencing) due to a complementary dsRNA molecule. Using Agrobacterium vectors, nematodespecific genes (DNA) were introduced into the host plant (Tobacco plant). The introduction of DNA produces both sense and anti-sense RNA in the host cells. These two RNA molecules being complementary to each other form a double stranded RNA (dsRNA) that initiates RNAi and thus, silences the specific mRNA of nematode. The consequence was that the parasite cannot survive in a transgenic host expressing specific interfering
RNA. 

Question. (a) Name the insect that attacks cotton crops and causes lot of damage to the crop.
How has Bt cotton plants overcome this problem and saved the crop? Explain.
(b) Write the role of gene Cry IAb.
Answer : (a) Cotton bollworm is the larvae that attack cotton crops.
Bt cotton plants are GMOs containing the active Cry gene from Bacillus thuringiensis, which form protein crystals during a particular phase of their growth. These crystals contain a toxic insecticidal protein.
These proteins are present in inactive protoxin form, but become active toxin in the alkaline pH of the insect gut.
The activated toxin binds to the surface of midgut epithelial cells and creates pores that cause cell swelling and lysis and eventually cause the death of the insect.
Specific Bt toxin genes were isolated from B. thuringiensis and genetically transferred to several crop plants such as cotton. Most Bt toxins are insect-group specific. The toxin is coded by a gene named cry.
(b) The protein coded by gene cryIAb controls corn borer. 

Question. Why GMOs are so called? List the different ways in which GMO plants have benefitted and have become useful to humans
Answer : Genetically Modified Organisms (GMO) or transgenic organisms are the plants, bacteria, fungi and animals whose genes are altered by manipulation.
Advantages of genetic modification in plants :
• It makes crops more tolerant to abiotic stresses like cold, drought, salt, heat etc. 
• Most of the GM plants have been developed for pest-resistance, which increases the crop productivity and therefore, reduces the reliance on chemical pesticides.
• It helps to reduce the post-harvest loss of crops.
• It increases the efficiency of mineral usage by plants. This prevents early exhaustion of the fertility of the soil.
• It enhances the nutritional value of food. This is known as bio-fortification. e.g.; Golden rice is transgenic variety in rice, which is rich in vitamin ‘A’.
• GM is used to create tailor-made plants to supply alternative resources to industries, in the form of starches, fuels and pharmaceuticals

Question. (a) Mention the cause of ADA deficiency in human
(b) How is gene therapy carried out to treat the patients suffering from this disease?
(c) State the probability of a permanent cure of this disease.
Answer : (a) The disease is caused by a mutation in a gene on chromosome 20. The gene codes for the enzyme ADA. It is an inherited disorder that
damages the immune system.
(b) ADA is very crucial for the immune system to function. The deficiency of ADA causes severe combined immunodeficiency disease. The patient lacks functional T-lymphocytes and fails to fight the infectious pathogens.
Using gene therapy, lymphocytes are extracted from the patient’s bone marrow and a normal functional gene for ADA is introduced into these lymphocytes with the help of the retrovirus.
The lymphocytes of bone marrow contain the functional ADA gene and reactivate the patient’s immune system.
(c) In some children, ADA deficiency can be cured by bone marrow transplantation, in others it can be treated by enzyme replacement therapy, in which functional ADA is given to the patient by injection. But the problem is that they are not completely cured. If the gene isolated from bone marrow cells producing ADA is introduced into cells at early embryonic stages, it could be a permanent cure. 

Question. What are transgenic animals ? How such animals are helpful to humans ?
Answer : Transgenic animals are those animals whose genome has been altered by the introduction of an
extra gene by manipulation, e.g., transgenic rats, rabbits, sheep, etc.
Benefits of transgenic animals are :
(i) Transgenic animals are produced to study how genes are regulated and how they affect the normal functions and development of the animal body.
(ii) Medicines are produced from transgenic animals, e.g., alpha-1-antitrypsin.
(iii) Transgenic animals are used to test vaccine safety before use in humans
(iv) Transgenic animals are designed to increase our understanding of how genes contribute to the development of diseases.

Question. What are some applications and advantages of stem cell technology ?
Answer : Applications of stem cells technology : Stem cells are special human cells which are able to develops into many different cell types. This can range from muscle cells to brain cells. In some cases they can also fix damage tissues. Stem cells are divided into two main forms. They are embryonic stem cells and adult stem cells. They are used in treating several clinical problems like :
(i) Tissue regeneration.
(ii) Damaged myocardium after heart infraction.
(iii) Brain after stroke.
(iv) Spinal cord after mechanical injury.
Advantages of stem cells :
(i) Adult stem cells have low rejection can rate.
(ii) Stem cells, having regenerative property can be used in replacing any organ, which is not working or failing.
(iii) They can help in studying human growth and cell development.
(iv) They can be used to test the effects of medicinal drugs and medicine without the use of animals.