CBSE Class 12 Biology Biotechnology and Its Application VBQs

Assertion and Reason Based MCQs

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) : Norman E. Borlaug was the father of “Green revolution”.
Reason (R) : Green revolution is the period when there is significant increase in agricultural productivity of grains (specially wheat and rice).
Answer : A

Question. Assertion (A) : Transgenic animals had their DNA manipulated.
Reason (R) : 95% of all existing transgenic animals are mice.
Answer : B

Question. Assertion (A) : Rosie was the first transgenic cow.
Reason (R) : It contained human alpha lactalbumin.
Answer : B

Question. Assertion (A) : Genetically modification make crops more tolerant to abiotic stress (cold, drought etc.)
Reason (R) : Genetically Modified Organisms (GMO) genes have been altered by manipulation.
Answer : A

Question. Assertion (A) : GEAC will decide the safety of introducing GM organism for public use.
Reason (R) : Genetic modifications of organisms may have opposite results when introduced into the ecosystem.
Answer : A

Question. Assertion (A) : RNAi takes place in all eukaryotic and prokaryotic organisms as a method of cellular defense.
Reason (R) : It prevents translation of a specific mRNA (silencing) due to a complementary dsRNA molecule.
Answer : D

Question. Assertion (A) : ‘Bt’ in Bt toxin represent Bacillus thuringiensis.
Reason (R) : ‘Bt’ toxin is produced by a virus.
Answer : C

Question. Assertion (A) : Transgenic mice are being used to test the safety of the polio vaccine.
Reason (R) : It could replace the use of monkeys to test the safety of batches of the vaccine.
Answer : A

Question. Assertion (A) : An American company allowed the company to sell a ‘new’ variety of Basmati rice.
Reason (R) : Indian Basmati was crossed with semi-dwarf varieties and claimed as a novelty.
Answer : B

Question. Assertion (A) : The inactive form of toxic proteins are advantageous to the bacteria producing it.
Reason( R) : Low concentration of a bacteria or virus, even at a time when the symptoms of the disease are not visible, can be detected.
Answer : B

Questions and Answers

Question. Explain the process of RNA interference.
Answer. Different steps involved in RNA silencing are as follows:
(i) Double-stranded RNAs are processed into approximately 21-23 nucleotide RNAs with two nucleotides. An RNase enzyme called Dicer cuts the dsRNA molecules (from a virus, transposon, or through transformation) into small interfering RNAs (siRNAs).
(ii) Each siRNA complexes with ribonucleases (distinct from Dicer) to form an RNA-induced silencing complex (RISC).
(iii) The siRNA unwinds and RISC is activated.
(iv) The activated RISC targets complementary mRNA molecules. The siRNA strands act as guides where the RISCs cut the transcripts in an area where the siRNA binds to the mRNA. This destroys the mRNA.
(v) When mRNA of the parasite is destroyed no protein is synthesised. It results in the death of the parasite in the transgenic host.

Question. How is Bt cotton made to attain resistance against bollworm?
Answer. Two genes cryIAc and cryIIAb control cotton bollworms. These two genes were isolated from Bacillus thuringiensis and incorporated into cotton plant. The genetically modified plant is called Bt cotton as it contains Bt toxin genes. The bacterium Bacillus thuringiensis produces Bt toxin proteins in mature form. When the insect larvae ingest any plant part, toxin becomes active in the alkaline pH of the gut and kills the insect pests. That is how Bt cotton attains resistance against bollworm.

Question. Nematode specific genes are introduced intothe tobacco plants using Agrobacterium vectors to develop resistance in tobacco plants against nematodes. Explain the events that occur in tobacco plant to develop resistance.
Answer. Using Agrobacterium vectors nematode specific genes are introduced into the tobacco plant. The introduction of DNA produces both sense and antisense RNA in tobacco plant cells. The two RNAs being complimentary to each other form dsRNA that initiates RNA interference.

Question. What is GMO? List any five possible advantages of a GMO to a farmer.
Answer. Bacteria, fungi, plants and animals whose genes have been altered by manipulation are called genetically modified organisms (GMO). 

Question. How has RNAi technique helped to prevent the infestation of roots in tobacco plants by a nematode Meloidogyne incognita?
Answer. A nematode Meloidogyne incognita infects the roots of tobacco plants and causes a great reduction in yield. Using Agrobacterium vectors, nematode- specific genes were introduced into the tobacco plant. The introduction of DNA was such that it produced both sense and antisense RNA in the host cells. These two RNAs being complementary to each other formed a double stranded RNA (dsRNA) that initiated RNA interference (RNAi) and thus, silenced the specific mRNA of the nematode. The result was that the parasite could not survive in a transgenic host expressing specific interfering RNA. The transgenic plant thus got itself protected from the parasite.

Question.How did the process of RNA interference help to control the nematode from infecting the roots of tobacco plants? 
Answer. A nematode Meloidogyne incognita infests the roots of tobacco plants and causes a great reduction in yield. A novel strategy that was adopted to prevent this infection was based on the process of RNA interference (RNAi). RNA interference (RNAi) is the phenomenon of inhibiting activity of a gene by synthesis of RNA molecules complementary to the mRNA. The normal (in vivo synthesised) mRNA of a gene is said to be “sense” because it carries the codons that are “read” during translation. Normally, the complement to the mRNA “sense” strand will not contain a sequence of codons that can be translated to produce a functional protein; thus, this complementary strand is called “anti-sense RNA”. The anti-sense  RNA and mRNA molecules will anneal to form duplex RNA molecules that can not be translated. Thus, the presence of anti-sense RNA will block translation of the mRNA of the affected gene. The source of this complementary RNA could be from an infection by viruses having RNA genomes or mobile genetic elements (transposons) that replicate via an RNA intermediate. Using Agrobacterium vectors, nematode-specific anti-sense genes are introduced into the host plant. The introduction of DNA produces anti-sense RNA in the host cells. The transgenic host plants expresses anti-sense RNA. As in consequence, nematode infestation fails in the transgenic plants because the complementary anti-sense RNA forms a double stranded RNA (ds RNA) which interferes or blocks the translation and thus, silences the mRNA of the nematode. The result was that the parasite could not survive in transgenic plant. In such way, the transgenic plant gets protected from the parasite.

Question. Name the pest that destroys the cotton bolls.
Explain the role of Bacillus thuringiensis in protecting the cotton crop against the pest to increase the yield.
Answer. The pest that destroy the cotton bolls are cotton bollworms.
Two genes cryIAc and cryIIAb control cotton bollworms. These two genes were isolated from Bacillus thuringiensis and incorporated into cotton plant. The genetically modified plant is called Bt cotton as it contains Bt toxin genes. The bacterium Bacillus thuringiensis produces Bt toxin proteins in mature form. When the insect larvae ingest any plant part, toxin becomes active in the alkaline pH of the gut and kills the insect pests. That is how Bt cotton attains resistance against bollworm.

Question. Name the vector used for introducing the nematode specific gene in tobacco plant.
Answer. Agrobacterium vectors are used for introducing nematode specific gene in tobacco plant.

Question. What are cry proteins? Name an organism that produces it. How has man exploited this protein to his benefit? 
Answer. The bacterium Bacillus thuringiensis is a common soil bacterium which produces a protein toxin that kills certain insects. The toxin is a crystal (cry) protein. There are several kinds of cry proteins which are toxic to different groups of insects. The gene encoding cry protein is called cry gene. Biotechnologists have been able to isolate the gene responsible for production of toxin and introduce it into a number of plants to produce genetically modified plants resistant to insects, e.g., Bt cotton (resistant to bollworm) and GM tobacco (resistant to hornworms).

Question. Why is Agrobacterium mediated genetic transformation described as natural genetic engineering in plants? 
Answer. The vector used to introduce new genes into plant cells is most often a plasmid from the soil bacterium Agrobacterium tumefaciens. In nature this bacterium infects all broad-leaved agricultural crops such as tomato, soybean, sunflower and cotton etc. and induces formation of cancerous growth called a crown gall tumour. This transformation of plant cells is due to the effect of Ti plasmid carried by the pathogenic bacterium. Hence, is called natural genetic engineer. For genetic engineering purposes, Agrobacterium strains are developed in which tumor-forming genes are deleted. These transformed bacteria can still infect plant cells.

Question. Explain the application of biotechnology in producing Bt cotton.
Answer. Bt cotton is produced by using biotechnology. Soil bacterium Bacillus thuringiensis produces proteins that kill certain insects like lepidopterans (tobacco budworm, armyworm), coleopterans (beetles) and dipterans (flies, mosquitoes) etc. B. thuringiensis forms some protein crystals. These crystals contain a toxic insecticidal protein. This toxin does not kill the bacteria because it exists as inactive protoxins in them. But, once an insect ingests the crystals, it is converted into an active form of toxin due to the alkaline pH of its alimentary canal that solublises the crystals.
Through genetic engineering Bt toxin genes were isolated from Bacillus thuringiensis and incorporated into the several crop plants such as cotton. The choice of genes depends upon the crop and targeted pest, as most Bt toxins are insect-group specific. The toxin is coded by a gene named cry. Two cry genes cryIAc and cryIIAb have been incorporated in cotton. The genetically modified crop is called Bt cotton as it contains Bt toxin genes against cotton bollworms. Similarly, cryIAb has been introduced in Bt corn to protect the same from corn borer.

Question. Why are certain cotton plants called Btcotton plants?
Answer. Cotton plants resistant to insect pests, e.g., cotton bollworms are produced through genetic engineering by the introduction of Bt toxin genes. These genes are cryIAc and cryIIAb.

Question. Suggest any two possible treatments that can be given to a patient exhibiting adenosine deaminase deficiency.
Answer. The possible treatments that can be given to a patient exhibiting adenosine deaminase (ADA) deficiency are:
(i) bone marrow transplantation
(ii) enzyme replacement therapy.

Question. Why do children cured by enzyme-replacement therapy for adenosine deaminase deficiency need periodic treatment?
Answer. The lymphocytes are not immortal. They have a life span, hence with the formation of new lymphocytes, the patient requires the periodic enzyme replacement therapy.

Question. State the role of C peptide in human insulin.
Answer. The C-peptide joins the A-peptide with B-peptide in the proinsulin. It is not present in mature insulin and is removed during processing of proinsulin to insulin.

Question.  How is proinsulin different from functional insulin in humans? 
Answer. Proinsulin has three polypeptide chains (A, B and C) whereas functional insulin has only two polypetide chains (A and B).

Question. Name any two techniques that serve the purpose of early diagnosis of some bacterial/viral disease. 
Answer. Recombinant DNA technology, polymerase chain reaction (PCR) and enzyme linked immuno- sorbent assay (ELISA) are the some of the techniques that serve the purpose of early diagnosis of bacterial/ viral diseases.

Question. How two short polypeptide chains of insulin are linked together? 
Answer. Insulin consists of two short polypeptide chains : A and B, that are linked together by two disulphide bridges.

Question. Suggest any two techniques which can help in early detection of bacterial/viral infection much before the symptom appear in the body.
Answer. Recombinant  DNA  technology, polymerase chain reaction (PCR) and enzyme linked immuno- sorbent assay (ELISA) are the some of the techniques that serve the purpose of early diagnosis of bacterial/ viral diseases.

Question. What is gene therapy? Name the first clinical case in which it was used. 
Answer. Gene therapy is the technique of genetic engineering which involves replacement of a faulty gene by a normal healthy functional gene. The first clinical gene therapy was given in 1990 to a 4 years old girl with adenosine deaminase deficiency (ADA deficiency). This enzyme is very important for the immune system to function

Question. Why is proinsulin so called? How is insulin different from it? 
Answer. Proinsulin is the prohormone which needs to be processed before it becomes a fully mature and functional hormone. Proinsulin contains an extra stretch called the C peptide. This C peptide is not present in the mature insulin and is removed during maturation into insulin.

Question. Write the functions of adenosine deaminase enzyme. State the cause of ADA deciency in humans. Mention a possible permanent cure
for an ADA deficiency patient.
Answer. Adenosine deaminase enzyme is necessary for the proper functioning of our immune system. ADA deficiency is caused by the defect in the gene coding for enzyme adenosine deaminase

Question. Expand the following and mention one application of each.
(a) PCR (b) ELISA
Answer. (a) PCR is polymerase chain reaction. It is used to detect HIV infection and mutations in genes in suspected cancer patient.
(b) ELISA is Enzyme- Linked Immunosorbent
Assay It is used to detect infections by pathogens.

Question. Describe the gene therapy procedure for an ADA-deficient patient.
Answer. The first step towards gene therapy for an ADA deficient patient is extraction of lymphocytes. Lymphocytes, a kind of white blood cells, are extracted from the bone marrow of the patient and are grown in a culture outside the body. A functional ADA cDNA (using a retroviral vector) is then introduced into these lymphocytes, which are reinjected to the patient’s bone marrow.

Question. List any two molecular diagnostic techniques and write one application of each of them.
Answer. (a) PCR is polymerase chain reaction. It is used to detect HIV infection and mutations in genes in suspected cancer patient.
(b) ELISA is Enzyme- Linked Immunosorbent
Assay It is used to detect infections by pathogens.

Question. How is recombinant DNA technology helping in detecting the presence of mutated gene in cancer patients? 
Answer. PCR is used to detect mutations in gene in suspected cancer patient. A single stranded DNA or RNA joined with a radioactive molecule (probe) is allowed to hybridise to its complementary DNA in a clone of cells. It is followed by detection using autoradiography. The clones having the mutated gene will not appear on the photographic film, because the probe will not have the complementarity with the mutated gene.

Question. Why is the introduction of genetically engineered lymphocytes into an ADA deficiency patient not a permanent cure? Suggest a possible permanent cure. 
Answer. In gene therapy, genetically engineered lymphocytes are introduced into an ADA deficiency patient. But as these cells do not always remain alive, the patient requires periodic infusion of such genetically engineered lymphocytes. However, if the isolated gene from bone marrow cells producing ADA is introduced into cells at early embryonic stages, it can be a permanent cure.

Question. How did Eli Lilly synthesise the human insulin? Mention one difference between this insulin and the one produced by the human pancreas.
Answer. Human insulin is made up of 51 amino acids arranged in two polypeptide chains, chain A having 21 amino acids and chain B with 30 amino acids. The two polypeptide chains are interconnected by two disulphide bridges or S-S linkages. In mammals, including humans, insulin is synthesised as a pro- hormone which contains an extra stretch called the C peptide. This C peptide is not present in the mature insulin and is removed during maturation into insulin. The main challenge for production of insulin using rDNA technique was getting insulin assembled into a mature form.
In 1983, Eli Lilly an American company, first prepared two DNA sequences corresponding to A and B chains of human insulin and introduced them in plasmids of Escherichia coli to produce insulin chains. Chains A and B were produced separately, extracted and combined by creating disulfide bonds to form human insulin (humulin). It is recombinant DNA technological process. Therefore, the difference between humulin (insulin synthesised by Eli Lilly) and insulin produced by the human pancreas is that humulin consists of two polypeptide chains (A and B) produced separately, extracted and combined by creating disulfide bond while insulin produced by human pancreas contains chains A, B and C and during maturation chain C is removed.

Question. Mention the advantage of these techniques over conventional methods.
Answer. Using conventional methods of diagnosis like serum and urine analysis etc., early detection of pathogen is not possible. But molecular diagnostic techniques serve the purpose of early diagnosis.

Question. Expand ELISA. On what principle is ELISA test based? List two ways by which an infection can be detected by this test. 
Answer. ELISA stands for Enzyme Linked Immunosor- bent Assay. ELISA is based on the principle of antigen
- antibody interaction. Infection by pathogen can be detected by the presence of very small amount of proteins, glycoproteins, etc. or by detecting the antibodies synthesised against the pathogen.

Question. Explain enzyme- replacement therapy to treat adenosine deaminase deficiency. Mention two disadvantages of this procedure. 
Answer. Adenosine deaminase (ADA) enzyme is crucial for the immune system to function. Its deficiency is caused due to the deletion of the gene for adenosine deaminase. In some patients, ADA deficiency can be cured by the bone marrow transplantation. It can be treated by enzyme replacement therapy, in which functional ADA is given to the patient by injection. Two disadvantages of enzyme replacement therapy are :
(i) It is not permanent cure because the replacement patient of ADA deficiency do not have functional T-lymphocytes, they cannot provide immune responses against invading pathogens.
(ii) It is a costly method.

Question. 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 insulin.
Answer. The recombinant DNA technology process has made great impact in the area of health care by mass production of safe and more effective therapeutic drugs. Further, the recombinant therapeutics do not induce unwanted immunological responses.

Question. ‘Plasmid is a boon to biotechnology’. Justify this statement quoting the production of human insulin as an example. 
Answer. Plasmids are extra-chromosomal, self repli- cating, usually circular, double-stranded, DNA molecules found naturally in many bacteria.
Plasmid is a boon to biotechnology. It has certain characteristics which make it a good vector in production of human insulin. These are discussed as follows :
(i) It has specific restriction sites where the enzyme restriction endonucleases make a cut and segment of DNA which codes for human insulin is inserted.
(ii) It has number of orgin of replication (ori) where replication starts.
(iii) Recombinant plasmid is introduced into E.coli host cell where it replicates and produces large amount of insulin.

Question. What is meant by ADA deficiency? How is gene therapy a solution to this problem? Why is it not a permanent cure? 
Answer. ADA deficency refers to deficiency of enzyme ADA (Adenosine deaminase) which is caused due to deletion of the gene for adenosine deaminase. 

Question. Name the source from which insulin was extracted earlier. Why is this insulin no more used by diabetic people?
Answer. Earlier insulin was extracted from pancreas of slaughtered cattle and pig. This insulin is not in use, as some diabetic patients developed allergic reaction to it.

Question. Briefly explain the principle, procedure and role of ELISA. 
Answer. Enzyme-linked immunosorbent assay (ELISA) is a non-isotopic immunoassay. ELISA is based on the immunochemical principles of antigen antibody reaction. It is more rapid and simple process hence is recommended for detection of antigens. The stages of ELISA are summarised as follows:
The antibody against the protein to be determined is fixed on an inert solid such as polystyrene. The biological sample containing the protein to be estimated is applied on the antibody coated surface. The protein antibody complex is then reacted with a second protein specific antibody to which an enzyme is covalently linked. Peroxidase, amylase and alkaline phosphatase are commonly used. After washing the unbound antibody linked enzyme, the enzyme bound to the second antibody complex is assayed. The enzyme activity is determined by its action on a substrate to form a product (usually coloured). This is related to the concentration of the protein being estimated.
ELISA is widely used for the determination of small quantities of proteins (hormones, antigens, antibodies) and other biological substances.
The most commonly used pregnancy test for the detection of human chorionic gonadotropin (hCG) in urine is based on ELISA. ELISA is also been used for diagnosis of HIV viruses in AIDS patient.

Question. What are transgenic animals? Give an example.
Answer. Transgenic animals are those animals which contain in their genome, a foreign gene introduced by recombinant DNA technology. Such gene is called transgene. Examples of transgenic animals are transgenic mice and transgenic rabbit etc.

Question. What was the speciality of the milk produced by the transgenic cow, Rosie? 
Answer. The first transgenic cow, Rosie, produced human protein enriched milk which contained the human alpha lactalbumin and was nutritionally more balanced product for human babies than natural cow milk.

Question. How have transgenic animals proved to be beneficial in:
(a) Production of biological products
(b) Chemical safety testing 
Answer. (a) Transgenic animals that produce useful biological products can be created by the introduction of the DNA segment (or gene) which code for a particular product such as human protein (α-1-antitrypsin) used to treat emphysema. Similar attempts are being made for treatment of phenylketonuria (PKU) and cystic fibrosis.
(b) Transgenic animals are being made that carry genes which make them more sensitive to toxic substances than non-transgenic animals. They are then exposed to the toxic substances and the effects are studied.

Question. Mention any four benefits derived from transgenic animals. 
Answer. Benefits derived from transgenic animals are as follows:
(i) They are specially made to serve as models for human diseases, so that investigation of new treatments for diseases is made possible.
(ii) They produce useful biological products, that can be created by introduction of portion of gene, which codes for a particular product such as human protein ( -1- antitrypsin) used to treat emphysema.
(iii) Transgenic mice are being developed for use in testing the safety of vaccine before they are used in humans.
(iv) They carry genes which make them more sensitive to toxic substances than non-transgenic animals. They are then exposed to toxic substance and the effects are studied.

Question. How is ‘Rosie’ considered different from a normal cow? Explain. 
Answer. Rosie is the first transgenic cow which contains human gene coding for protein alpha-lactalbumin. The gene is expressed in mammary tissues and the protein is secreted in milk. This milk is nutritionally a more balanced product for human babies than natural cow milk.

Question. Highlight any four advantages of genetically modified organisms  
Answer. Advantages of genetically modified organisms are as follows:
(i) Genetically modified organisms such as mice are being formed for use in testing the safety of vaccines before they are used on human beings. Transgenic mice are being used to test the safety of the polio vaccine.
(ii) Several bacteria have been modified by introduction of foreign genes to control, (i) insects by prodcution of endotoxins, (ii) fungal diseases by production of chitinases, which suppress fungal flora in the soil and (iii) by production of antibiotic which will degrade the toxin produced by pathogen.
(iii) Genetically modified organisms are developed that carry genes exposed to the toxic substance and their effects are studied.
(iv) Genetically modified plants have higher
nutritional value e.g., golden rice is rich in vitamin A.

Question. Mention two objectives of setting up GEAC by our Government. 
Answer. GEAC is Genetic Engineering Approval
Committee. It makes decisions regarding the validity of GM research and the safety of introducing GM organisms for public services. The objectives of setting up GEAC by our government is as follows:
(i) To permit the use of GM organisms and their products for commercial applications.
(ii) To adopt procedures for restriction, production, import, export and application of GM organisms. (iii) To approve for conduct of large scale field trials and release of transgenic crops in the environment. (iv) To authorise agencies or persons to have large scale production and release of GM organisms into the environment or curb and take punitive action against them.

Question. What is biopiracy? 
Answer. Biopiracy refers to the exploitation or patenting of biological resource of a nation by some organisations or multinational companies without proper authorisation from the concerned countries.

Question. Name the Indian variety of rice patented by an American company. 
Answer. Indian variety of rice patented by American company Rice Tec Inc in 1997 was basmati rice

Question. A multinational company outside tried to sell new varieties of turmeric without proper patent rights. What is such an act referred to?
Answer. The use of bioresources by multinational companies and other organisations without proper authorisation from the countries and people concerned without compensatory payment is called as biopiracy.

Question. (a) What is biopiracy?
(b) State the initiative taken by the Indian parliament against it. 
Answer. The Indian parliament has recently passed the second amendment of the Indian patent bill that considers issue related to patent terms, emergency provisions and research and development initiative.

Question. Biopiracy should be prevented. State why and how?
Answer. Some multinational companies of industrialised nations have a good economic status but are poor in biodiversity and are exploiting biodiversity of developing and underdeveloped countries without authorisation and proper compensation.
There has been growing realisation of the injustice,inadequate compensation and benefit sharing between developed and developing countries. Therefore, some nations are developing laws to prevent such unauthorised exploitation of their bio- resources and traditional knowledge.