1. What triggers the activation of protoxin to active toxin of Bacillus thuringiensis in boll worm?
(a) Acidic pH of stomach
(b) Body temperature
(c) Moist surface of midgut
(d) Alkaline pH of gut
1. (d) : Some strains of Bacillus thuringiensis produce proteins that kill certain insects such as lepidopterans and dipterans. B. thuringiensis forms protein crystals during a particular phase of their growth. These crystals contain a toxic insecticidal protein which exists as inactive protoxins but once an insect ingest the inactive toxin, it is converted into an active form of toxin due to the alkaline pH of the gut which solubilises the crystals.
2. Which of the following is true for Golden rice?
(a) It has yellow grains, because of a gene introduced from a primitive variety of rice.
(b) It is vitamin A enriched, with a gene from daffodil.
(c) It is pest resistant, with a gene from Bacillus thuringiensis.
(d) It is drought tolerant, developed using Agrobacterium vector.
2. (b) : Rice is a staple food in many countries, particularly in Asia, but does not contain vitamin A or its immediate precursors. By inserting two genes from daffodil and one gene from a bacterial species into rice plants, Swiss researchers have produced rice capable of synthesising b-carotene, the precursor of vitamin A. Vitamin A is required by all individuals as it is present in retina of eyes. Deficiency of vitamin A causes night blindness and skin disorders. This rice is called ‘Golden rice’ because of yellow colour of rice grains due to the presence of b-carotene.
3. In RNAi, the genes are silenced using
(a) dsRNA (b) ssDNA
(c) ssRNA (d) dsDNA.
3. (a) : RNAi or RNA interference is a novel strategy which prevents the infection by nematode Meloidogyne incognita in the roots of tobacco plants. RNAi involves silencing of specific mRNA. Using Agrobacterium vectors, nematode specific genes are introduced into the host plant (tobacco plant). The introduction of DNA is such that it produces both sense and anti-sense RNA in the host cells. These two RNAs, being complementary to each other form a dsRNA (double stranded RNA), that initiates RNAi by first forming siRNA (small interfering RNAs). The siRNA first unwinds and then binds to specific complementary mRNA molecules of the nematode. These sites are then cut by RISC (RNA-induced silencing complex), thereby destroying mRNA of host. Hence, no toxin proteins are synthesised.
4. Identify the incorrect statement regarding Bt cotton.
(a) Dried spores of Bacillus thuringiensis are sprayed on its vulnerable leaves.
(b) It releases toxin that causes swelling in the gut of insect that ingest its leaves.
(c) It is a transgenic plant.
(d) It can produce toxin due to gene introduced in it by transgenesis.
4. (a)
5. The plasmid of which one of the following has ‘nif’ gene in it?
(a) Rhizobium
(b) Agrobacterium tumefaciens
(c) Bacillus thuringiensis
(d) Salmonella typhimurium
5. (a) : The nif gene is a nitrogen fixing gene found in bacterium Rhizobium.
6. The introduction of T-DNA into plants involves
(a) exposing the plants to cold for a brief period
(b) allowing the plant roots to stand in water
(c) infection of the plant by Agrobacterium tumefaciens
(d) altering the pH of the soil, then heatshocking the plants.
Ans. (c) : Ti plasmid (tumor inducing) from the soil bacterium Agrobacterium tumefaciens is effectively used as vector for gene transfer to plant cells. The part of Ti plasmid transferred into plant cell DNA, is called the T-DNA. This T-DNA with desired DNA spliced into it, is inserted into the chromosomes of the host plant where it produces copies of itself, by migrating from one chromosomal position to another at random. Such plant cells are then cultured, induced to multiply and differentiate to form plantlets. Transferred into soil, the plantlets grow into mature plants, carrying the foreign gene, expressed throughout the new plant.
7. Protein encoded by gene cryIAb controls the infestation of which of the following insects?
(a) Cotton bollworm (b) Anopheles mosquito (c) Corn borer (d) Aedes mosquito
7. (c) : Protein encoded by gene cryIAb controls the infestation of corn borer insects in Bt corn.
8. RNA interference which is employed in making tobacco plant resistant to Meloidogyne incognita is essentially involved in
(a) preventing the process of replication of DNA
(b) preventing the process of translation of mRNA
(c) preventing the process of splicing of hnRNA
(d) preventing the process of transcription.
8. (b)
9. Which of the following Bt crops is being grown in India by the farmers?
(a) Brinjal (b) Soybean (c) Maize (d) Cotton
9. (d)
10. Consumption of which one of the following foods can prevent the kind of blindness associated with vitamin ‘A’ deficiency?
(a) ‘Flavr Savr’ tomato (b) Canolla
(c) Golden rice (d) Bt-brinjal
10. (c)
11. Bt brinjal is an example of transgenic crops.
In this, Bt refers to
(a) Bacillus tuberculosis
(b) biotechnology
(c) b-carotene
(d) Bacillus thuringiensis.
11. (d)
12. The genetically-modified (GM) brinjal in India has been developed for
(a) insect-resistance
(b) enhancing shelf life
(c) enhancing mineral content
(d) drought-resistance.
12. (a) : The genetically modified (GM) Bt brinjal in India has been developed mainly for insect resistance. Through genetic engineering Bt toxin genes were isolated from Bacillus thuringiensis and incorporated into the several crop plants such as cotton, brinjal etc.
13. Some of the characteristics of Bt cotton are
(a) long fibre and resistance to aphids
(b) medium yield, long fibre and resistance to beetle pests
(c) high yield and production of toxic protein crystals which kill dipteran pests
(d) high yield and resistance to bollworms.
13. (d) : Bt toxin genes were isolated from Bacillus thuringiensis and incorporated into cotton plant. The genetically modified crop is called Bt cotton. Bt cotton has the following useful characteristics: pest resistance, herbicide tolerance, high yield and resistance to boll worm infestation.
14. An improved variety of transgenic basmati rice
(a) does not require chemical fertilisers and growth hormones
(b) gives high yield and is rich in vitamin A
(c) is completely resistant to all insect pests and diseases of paddy
(d) gives high yield but has no characteristic aroma.
14. (b)
15. cryIIAb and cryIAb produce toxins that control
(a) cotton bollworms and corn borer respectively
(b) corn borer and cotton bollworms respectively
(c) tobacco budworms and nematodes respectively
(d) nematodes and tobacco budworms respectively
15. (a)
16. Which of the following is commonly used as a vector for introducing a DNA fragment in human lymphocytes?
(a) Retrovirus (b) Ti plasmid (c) l phage (d) pBR322
16. (a) : Retroviruses cause cancer in animals including humans. So modified retroviruses are used to transfer desirable genes into animal cells. It is used in gene therapy, in which lymphocytes from blood of patient are grown in culture medium outside the body, a functional gene is introduced by using a retroviral vector into these lymphocytes.
17. Which kind of therapy was given in 1990 to a four-year-old girl with adenosine deaminase (ADA) deficiency?
(a) Gene therapy
(b) Chemotherapy
(c) Immunotherapy
(d) Radiation therapy
17. (a) : Gene therapy is a technique of genetic engineering which involves replacement of a faulty/disease causing gene by a normal healthy functional gene. The first clinical gene therapy was given in 1990 to a 4-year old girl with adenosine deaminase (ADA) deficiency. This enzyme is very important for the immune system to function. The deficiency of this enzyme can lead to severe combined immune deficiency (SCID).
18. Select the wrong statement.
(a) Human insulin is being commercially produced from a transgenic species of Escherichia coli.
(b) Bt toxin genes cryIAc control the corn borer.
(c) Human protein, a-1-antitrypsin is used to treat emphysema.
(d) The first transgenic cow, Rosie, produced alpha lactalbumin, enriched milk.
18. (b)
19. The first human hormone produced by recombinant DNA technology is
(a) insulin (b) estrogen (c) thyroxin (d) progesterone.
19. (a) : The recombinant DNA technological processes have made great impact in the area of health care by mass production of safe and more effective therapeutic drugs. 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).
20. The 51 amino acids of insulin are arranged in
(a) single polypeptide
(b) two polypeptides, having 21 and 30 amino acids in chain A and B respectively
(c) two polypeptides having 25 and 26 amino acids
(d) two polypeptides having 18 and 33 amino acids.
20. (b) : 51 amino acids of insulin are arranged in two polypeptide chains, chain A having 21 amino acids and chain B having 30 amino acids. The two polypeptide chains are interconnected by two disulphide bridges.
21. How many recombinant therapeutics have been used for human diseases throughout the world?
(a) 12 (b) 24 (c) 30 (d) 56
21. (c)
22. Which one of the following vectors is used to replace the defective gene in gene therapy?
(a) Adenovirus (b) Cosmid (c) Ri plasmid (d) Ti plasmid
22. (a) : Gene therapy is a corrective therapy that is given to patients of diseases caused by some gene defects. Here, genes are inserted into a person’s cells and tissues to treat disease by replacing the defective gene. The normal gene delivered into the individual or embryo takes over the function of and compensate for the normal gene. Viral vectors like adenovirus are generally used to deliver the normal gene.
23. Human proteins can be produced in the milk or semen of farm animals. True or false?
(a) True
(b) False, proteins cannot be produced in milk
(c) False, proteins cannot be produced in semen
(d) False, animals are not used for protein production
23. (a) : Several human genes have been successfully transferred in animals and are expressed in the mammary tissue; the protein is secreted in milk from where it is easily harvested. These genes can also be made to express in reproductive tissues and thus proteins can also be harvested from semen ejaculate of male organisms. E.g., hGH is being produced from a transgenic mouse variety’s semen.
24. The genetic defect, adenosine deaminase (ADA) deficiency may be cured permanently by
(a) administering adenosine deaminase through injection
(b) bone marrow transplantation
(c) enzyme replacement therapy
(d) introducing isolated gene from marrow cells producing ADA into the cells at early embryonic stages
24. (d) : Adenosine deaminase enzyme is crucial for the immune system to function. The disorder ADA deficiency is caused due to deletion of the gene for adenosine deaminase.
ADA deficiency can be cured by bone marrow transplantation or by enzyme replacement therapy, in which functional ADA is given to the patient by injection. But both of these approaches are not completely curative as the patient requires periodic infusion of such genetically engineered lymphocytes or hormonal injections. However, if the gene isolated from marrow cells producing ADA is introduced into cells at early embryonic stages, it could be a permanent cure.
25. During the processing of the prohormone “proinsulin” into the mature “insulin”
(a) C-peptide is added to proinsulin
(b) C-peptide is removed from proinsulin
(c) B-peptide is added to proinsulin
(d) B-peptide is removed from proinsulin.
25. (b) : Human insulin is made up of 51 amino acids arranged in two polypeptide chains, A having 21 amino acids and B with 30 amino acids. The hormone develops from a storage product called pro-insulin. Pro-insulin has three chains, A, B and C. C – chain with 33 amino acids is removed prior to insulin formation. This C peptide is not present in the mature insulin and is removed during maturation into insulin.
32. (b) : Animals that have their DNA manipulated to possess and express an extra (foreign) gene are known as transgenic animals. Transgenic mice, rabbits, pigs, sheep, cows and fish have been produced, although over 95 per cent of all existing transgenic animals are mice.
34. (d) : Indian Government has set up organisation such as GEAC (Genetic Engineering Approval Committee) which makes decisions regarding the validity of GM research and safety of introducing GM organisms for public services.
35. (d) : In 1997, a Texas company got patent rights on Basmati rice through the US Patent and Trademark Office. This allowed the company to sell a ‘new’ variety
of Basmati, in the US and abroad. This new variety of Basmati had actually been derived from Indian farmers’ varieties. Indian Basmati was crossed with semi-dwarf varieties and claimed as an invention or a novelty. It caused a brief diplomatic crisis between India and United States with India threatening to take the matter to WTO (World Trade Organisation) as a violation of TRIPS (Trade Related Aspects of Intellectual Property Rights). Both voluntarily and due to review decisions by United States patent office, Rice Tec lost most of the claims of the patent.
(a) somatic cell
(b) vegetative cell
(c) germ cell
(d) body cell.
Case Based MCQs
Case I : Read the following passage and answer the questions from 41 to 45 given below.
Insulin used to cure diabetes was earlier extracted from pancreas of slaughtered cattle and pigs. Insulin extracted from an animal source, though caused some patients to develop allergy or other types of reactions to the foreign protein. Human insulin consists of two short polypeptide chains : chain A and chain B, that are linked together by disulphide bridges. 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 mature insulin and is removed during maturation into insulin.
41. Identify A in the given figure.
(a) Polypeptide chain A
(b) Polypeptide chain B
(c) Polypeptide chain C
(d) None of these
41. (c) : A represents polypeptide chain C which is removed prior to insulin formation.
42. The following is a list of some stages involved in producing human insulin from genetically engineered bacteria.
1. The bacteria are cultured in a fermenter for large scale production.
2. Recombinant insulin is extracted from the bacterial cells that expresses insulin gene.
3. The same restriction enzyme is used again to cut the bacterial plasmid for insertion of the human insulin gene.
4. Bacteria take up the plasmid carrying the insulin gene.
5. A restriction enzyme is used to cut human DNA to extract the insulin gene.
Select the correct order of these stages.
(a) 1, 5, 3, 4, 2 (b) 2, 4, 3, 5, 1
(c) 4, 5, 3, 2, 1 (d) 5, 3, 4, 1, 2
42. (d)
43. To insert the insulin gene into bacterial DNA, both the bacterial plasmid and the human chromosome containing the insulin gene are treated with the same restriction enzyme. Using the same restriction enzyme ensures that
(a) DNA ligase is able to join the segments of human and bacterial DNA
(b) the exact length of nucleotides matching the insulin gene is removed from the plasmid
(c) both the bacterial and human DNA will contain sticky ends
(d) sticky ends in the cut plasmid and insulin gene are complementary.
43. (d) : Each particular restriction enzyme produces unique sticky ends. Using the same enzyme for both the bacterial and human DNA will produce complementary sticky ends that can bind together by complementary base pairing. This would allow the human insulin gene to be inserted into the plasmid.
44. Why is the fermentor important for the production of human insulin by transgenic bacteria?
(a) It provides optimal conditions for the transgenic to multiply rapidly.
(b) It facilitates the extraction and purification of insulin from the transgenic bacteria.
(c) It maximise the rate of fermentation of the transgenic bacteria.
(d) It provides the low-oxygen conditions that are important for insulin production.
44. (a) : The optimal temperature, pH, oxygen and nutrient conditions in the fermenter allow the bacteria containing the insulin gene to reproduce quickly and produce large quantities of it.
45. A bacteriologist carries out his first attempt at engineering E.coli with the gene for human insulin. During the process, he realises that his stock of DNA ligase has depleted but decides to continue anyway. What is a likely consequence of his decision?
(a) Bacteria with the rDNA will not be able to form colonies in a fermenter.
(b) The resulting plasmids are not able to enter the E.coli bacteria even after applying heat shock.
(c) The resulting E.coli bacteria do not contain the human insulin gene.
(d) The bacterial plasmids do not have sticky ends and are unable to accommodate the human gene.
Case II : Read the following passage and answer the questions from 46 to 50 given below.
Transgenic cows have extra gene or genes inserted into their DNA. Firstly the genes for the desired product is identified and sequenced. Then a gene construct containing this desired gene is introduced into female cow cells. Transgenic bovine cells are selected and fused with bovine oocytes that have had all of their chromosomes removed. Once fused with the oocyte, the transgenic cells chromosomes are reprogrammed to direct development which can be implanted into a recipient cow. The resulting transgenic cow only express the transgene in her milk. This is because expression of the transgene is controlled by a promoter specific to lactating mammary cells.
46. The gene construct with desired gene is introduced into female cow cells by
(a) transformation (b) transduction (c) transfection (d) transplantation.
46. (c)
47. Production of transgenic cow fulfill the objective of
(a) increased milk production
(b) increased meat production
(c) molecular farming
(d) all of these.
47. (d) : The two chief objectives of transgenic cow production are as follows : (i) increased milk and meat production and (ii) molecular farming.
48. The name of first transgenic cow is
(a) Tracy (b) Dolly (c) Rosie (d) ANDI.
48. (c)
49. Transgenic cow is produced through the implantation of ________ containing transgene into recipient cow.
(a) ova
(b) embryo
(c) mammary cell
(d) both (a) and (b)
49. (b) : Transgenic bovine cells are selected and fused with bovine oocytes that have had all its chromosomes removed. Once fused with oocyte, the transgenic cells chromosomes are reprogrammed to direct development into an embryo which is implanted into recipient cow.
50. Read the given statements and select the correct option.
Statement I : Transgenes only express in the mammary glands of transgenic cow. Statement II : Transgenes are present in chromosomes of every cell in transgenic cow.
(a) Both statements I and II are true.
(b) Both statements I and II are false.
(c) Statement I is true but statement II is false.
(d) Statement I is false but statement II is true
50. (a)
Assertion & Reasoning Based MCQs
For question numbers 51-60, two statements are given-one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
(a) Both assertion and reason are true and reason is the correct explanation of assertion.
(b) Both assertion and reason are true but reason is not the correct explanation of assertion.
(c) Assertion is true but reason is false.
(d) Assertion is false but reason is true.
51. Assertion : Transgenic food may cause toxicity or produce allergy.
Reason : Transgenic plants have high nutrient content.
51. (b) : Plant in which foreign genes have been introduced through genetic engineering are called transgenic plants. Transgenic food from such plants may cause toxicity and or produce allergies. The enzyme produced by the antibiotic resistance genes can cause allergies because it is a foreign protein. GM plants enhance nutritional value of food, e.g., Golden rice.
52. Assertion : Genetically modified microbes help in crop protection.
Reason : Transgenic bacteria control insects by producing endotoxins.
52. (b)
53. Assertion : Biopatents are awarded for biological entities and all products derived from them.
Reason : Patent on use of turmeric in wound healing was cancelled in 2008.
53. (c) : Biopatents are awarded for biological entities and all products derived from them. 1995 patent on ‘use of turmeric in wound healing’ was cancelled in 1998.
54. Assertion : Agrobacterium tumefaciens is popular in genetic engineering because this bacterium is associated with the roots of all cereal and pulse crops.
Reason : Agrobacterium tumefaciens, is pathogen of several dicot plants is able to cause crown gall tumors. These tumors are incited by the conjugative transfer of DNA segment (T DNA).
54. (d) : A. tumefaciens causes crown gall disease on a wide range of dicot (broad leaved) plants especially members of rose family by transferring its own DNA into plant cells. But in laboratory, the ability to move all sorts of genes into plants has made the microbe the standard tool for investigating plant genetics and modifying crops.
55. Assertion : Mouse is the most preferred mammal for studies on gene transfers.
Reason : Mouse possesses features like short oestrous cycle and gestation period, relatively short generation time, production of several offspring per pregnancy, etc.
55. (a) : Mouse is the most preferred mammal for studies on gene transfers due to its many favourable features like (i) short oestrous cycle and gestation period, (ii) relatively short generation time, (iii) production of several offspring per pregnancy, (iv) convenient in vitro fertilisation, successful culture of embryos in vitro.
56. Assertion : Agrobacterium tumefaciens is called natural genetic engineer.
Reason : Agrobacterium tumefaciens infects all broad-leaved agricultural crops but does not infect cereal crops.
56. (b) : Ti plasmid (tumor inducing) from Agrobacterium tumefaciens is effectively used as a vector for gene transfer to plant cells. In nature, it induces tumors in broad leaf crops, e.g., tomato, soybean, cotton, etc.
57. Assertion : ADA deficiency cannot be cured permanently by gene therapy.
Reason : The lymphocytes from the blood of patient are grown in culture outside the body.
57. (d) : As a first step towards gene therapy, 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. 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 permanent cure.
58. Assertion : PCR is routinely used for early diagnosis of HIV in suspected AIDS patients. Reason : PCR can detect low amounts of DNA.
58. (b)
59. Assertion : Flavr-Savr tomato was the first transgenic commercial crop that entered the market.
Reason : Roundup variety of soybean was prepared through breeding.
59. (c) : The Flavr-Savr tomato, was the first genetically modified fruit/vegetable to reach the market in USA. Roundup ready soybean is a genetically modified herbicide tolerant cultivar.
60. Assertion : Molecular probes are available for diagnosing genetic disorders, e.g., Duchenne muscular dystrophy, cystic fibrosis, Tay-sach’s disease.
Reason : The molecular probes are usually double stranded pieces of DNAs, labelled with radioisotopes such as 32P.
5. Two transgenic microorganisms used for large scale amino acid production are:
(i) Bacillus amyloliquefaciens
(ii) Lactobacillus casei
11. Transgenic crops or genetically modified crop contain and express one or more useful foreign genes or transgenes. Brassica napus is used to produce blood anticoagulant protein. The protein is called hirudin.
The protein hirudin is an anticoagulant which is present in leech. Its gene was chemically synthesized and introduced in Brassica napus. The seeds of the latter came to have hirudin which could be extracted and purified.
12. 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 bioresources and traditional knowledge.
13. (a) cryIAc gene controls cotton bollworms in Bt cotton.
(b) RNA interference (RNAi) takes place in all eukaryotic organisms as a method of cellular defense. This method involves silencing of a specific mRNA.
14. SCID stands for severe combined immunodeficiency disease. The SCID patient has a defective gene for the enzyme adenosine deaminase. He/she lacks functional T-lymphocytes and therefore fails to fight with infecting pathogens. It can be cured by gene therapy.
In SCID, the patient lacks functional T-lymphocytes and it is congenital while in AIDS only T-helper cells are destroyed by virus, but is not congenital.
16. 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).
(i) PCR is polymerase chain reaction. It is used to detect HIV infection and mutations in genes in suspected cancer patient. (ii) ELISA is Enzyme- Linked Immunosorbent Assay. It is used to detect infections by pathogens.
21. 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 curb and take punitive action against agencies if they disturb ecological balance.
22. Insulin consists of two short polypeptide chains: chain A and chain B, that are linked together by disulphide bridges. In mammals, including humans, insulin is synthesised as a prohormone 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 given diagram explains the maturation of proinsulin into insulin:
30. The steps in RNA interference (RNAi)
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.
36. (a) Benefits derived from transgenic animals are as follows:
(i) 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 (a -1- antitrypsin) from transgenic sheep is used to treat emphysema.
(ii) Transgenic mice are being developed for use in testing the safety of vaccine before they are used in humans.
(iii) They carry genes which make them more sensitive to toxic substances than non-transgenic animals. They are then exposed to toxic substances and the effects are studied.
(b) The ethical issues concerned with the production of transgenic animals include:
(i) Introduction of a transgene from one species into another species violates the ‘integrity of species’.
(ii) Transfer of human genes into animals (and vice-versa)
dilutes the concept of ‘humanness’.
(iii) When animals are used for production of pharmaceutical proteins, they are virtually reduced to the status of a ‘factory’.
(iv) Use of animals in biotechnology causes great suffering to them.
(v) It is disrespectful to living beings, and only exploits them for the benefit of human beings.
38. Enzyme-linked immunosorbent assay (ELISA) is a nonisotopic immunoassay. ELISA is based on the immunochemical principles of antigen antibody reaction. The stages of ELISA are summarized as follows:
(i) 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.
(ii) 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.
(ii) ANDI - DNA of a fluorescent jelly fish was introduced into an unfertilised egg of a Rhesus monkey in the test tube. The diploid egg underwent cleavage and the early embryo was implanted in a surrogate mother. It has been named ANDI, the acronym of “inserted DNA”. This work would be helpful for curing diseases such as breast cancer, Alzheimer’s disease, diabetes and AIDS.
(iii) Tracy, the transgenic ewe was born in Scotland. Transgenic sheep have been produced to achieve better growth and meat production. For example, human genes for blood clotting factor IX and for a1-antitryspin have been transferred in sheep and expressed in mammary tissue. This was achieved by fusing the genes with the mammary tissue-specific promoter of the bovine b-lactoglobulin gene. Human growth hormone gene has also been introduced in sheep in order to promote growth and meat production. However, they also showed several undesirable effects like joint pathology, skeletal defects, gastric ulcers, infertility, etc.
(b) Transgenic chicken is resistant to avian leukosis virus (ALV).
