NEET Biology: Biotechnology · Chapter 2

Biotechnology and its Applications

What to remember

Bt cotton carries cry genes from Bacillus thuringiensis. The Cry protein is an inactive protoxin that is activated in the alkaline gut of the insect, creates pores in midgut cells and kills the pest.
RNA interference (RNAi) silences a specific mRNA using complementary double-stranded RNA. It was used to protect tobacco plants from the nematode Meloidogyne incognita.
Human insulin was first made by recombinant DNA technology in 1983 by Eli Lilly. The A and B chains were made separately in E. coli and joined by disulphide bonds. In humans, insulin is made as proinsulin and the C peptide is removed.
PCR, ELISA and DNA probes help in early diagnosis. Gene therapy was first used in 1990 for ADA deficiency. Transgenic animals, such as Rosie the cow, give useful products. GEAC, patents and biopiracy are the main ethical and legal issues.

Applications in agriculture

There are three options for increasing food production: agro-chemical based agriculture, organic agriculture and genetically engineered crop-based agriculture. Chemical inputs are costly for farmers in developing countries. Genetically modified (GM) organisms are those whose genes have been altered by manipulation. GM crops are also called transgenic crops when a foreign gene is added.

Benefits of GM plants:

Benefit	Meaning
Tolerance to abiotic stresses	Crops made more tolerant to cold, drought, salt and heat
Reduced dependence on chemical pesticides	Pest-resistant crops are produced
Reduced post-harvest losses	Crops stay good for longer
Better use of minerals	Efficiency of mineral usage by plants increases, which prevents early exhaustion of soil fertility
Enhanced nutritional value	For example, vitamin A enriched rice (golden rice)
Tailor-made plants	Plants give alternative resources to industries, such as starches, fuels and pharmaceuticals

Bt cotton. Bacillus thuringiensis is a bacterium. It forms protein crystals during a particular phase of its growth. These crystals contain a toxic insecticidal protein, the Cry protein, also called Bt toxin. The toxin does not kill the bacterium, because it exists as an inactive protoxin inside the bacterium.

How the toxin works:

1. The insect eats the crystals with the plant.
2. The alkaline pH of the insect gut dissolves the crystals. The protoxin changes into the active toxin.
3. The active toxin binds to the surface of the midgut epithelial cells and creates pores.
4. The cells swell and burst (lyse), and the insect dies.

The toxin protein is coded by genes named cry. Specific Bt toxins kill specific insect groups.

Gene	Protein	Target pest
cryIAc	Cry protein	Cotton bollworms
cryIIAb	Cry protein	Cotton bollworms
cryIAb	Cry protein	Corn borer

Different Bt toxins are active against particular groups of insects: lepidopterans (tobacco budworm, armyworm), coleopterans (beetles) and dipterans (flies and mosquitoes). The cry gene is isolated from Bacillus thuringiensis and incorporated into the crop plant. The plant then makes its own toxin and is protected from the pest. A cotton plant with such a gene is Bt cotton.

Pest-resistant plants by RNA interference. Meloidogyne incognita is a nematode that infects the roots of tobacco plants and greatly reduces the yield. RNA interference (RNAi) is a method of cellular defence found in all eukaryotes. In RNAi, a specific mRNA is silenced by a complementary double-stranded RNA (dsRNA) molecule that binds to the mRNA and prevents its translation. This is called silencing. The source of complementary RNA could be an infection by an RNA virus or mobile genetic elements (transposons) that replicate through an RNA intermediate.

Using Agrobacterium vectors, nematode-specific genes were introduced into the host plant. The DNA introduced produced both sense and anti-sense RNA in the host cells. These two RNAs are complementary to each other. They formed a double-stranded RNA that started RNAi and silenced a specific mRNA of the nematode. The parasite could not survive in a transgenic host that expressed the specific interfering RNA. The transgenic plant was thus protected from the parasite.

Applications in medicine

Recombinant DNA technology makes safe and effective therapeutic drugs on a large scale. The recombinant drugs are identical to the human proteins and do not cause unwanted immune responses. Over 30 recombinant therapeutic drugs have been approved for human use in the world.

Genetically engineered insulin. Adult-onset diabetes is controlled by taking insulin at regular intervals. Earlier, insulin was extracted from the pancreas of slaughtered cattle and pigs. It could cause allergy or other reactions in some patients.

Insulin has two short polypeptide chains: chain A and chain B. They are linked together by disulphide bridges. In mammals, including humans, insulin is first synthesised as a prohormone called proinsulin. Proinsulin has an extra stretch called the C peptide. The C peptide is removed during maturation into insulin.

In 1983, the company Eli Lilly prepared two DNA sequences corresponding to the A and B chains of human insulin. It introduced them into plasmids of E. coli to produce the chains. The chains A and B were produced separately, extracted and combined by creating disulphide bonds to form human insulin.

Feature	Old source	Recombinant source
Source	Pancreas of cattle and pigs	E. coli carrying the human A and B chain sequences
Reaction in patient	Possible allergy	Identical to human insulin
Chains	Taken as a whole hormone	A and B chains made separately and joined by disulphide bonds

Gene therapy. Gene therapy is a collection of methods that allow correction of a gene defect that has been diagnosed in a child or embryo. Genes are inserted into a person's cells and tissues to treat a hereditary disease. The defective gene is compensated by providing a normal gene.

The first clinical gene therapy was given in 1990 to a four-year-old girl with adenosine deaminase (ADA) deficiency. This enzyme is crucial for the working of the immune system. The disorder is caused by the deletion of the gene for adenosine deaminase. The ways of treatment are:

Bone marrow transplantation in some patients.
Enzyme replacement therapy, in which functional ADA is injected into the patient.
Gene therapy, as described below.

In the gene therapy method, lymphocytes from the blood of the patient are grown in a culture outside the body. A functional ADA cDNA, using a retroviral vector, is then introduced into these lymphocytes. The lymphocytes are subsequently returned to the patient. These cells are not immortal, so the patient needs periodic infusions of such genetically engineered lymphocytes. If the gene isolated from marrow cells that make ADA is introduced into cells at an early embryonic stage, it could be a permanent cure.

Molecular diagnosis. Early detection is not possible by conventional methods such as serum and urine analysis. Early diagnosis of a disease helps in effective treatment. The tools are:

Tool	Principle	Use
PCR	Amplifies nucleic acid, so a very low amount of pathogen DNA or RNA can be detected	Detection of HIV in suspected AIDS patients; detection of mutations in genes in suspected cancer patients; detection of bacteria or viruses at an early stage of infection
Recombinant DNA probe	A single-stranded DNA or RNA tagged with a radioactive molecule hybridises to its complementary DNA in a clone of cells. Detection is by autoradiography	Detection of a mutated gene. A clone with the mutated gene will not appear on the photographic film, because the probe does not have complementarity with the mutated gene
ELISA (enzyme-linked immunosorbent assay)	Antigen-antibody interaction	Infection is detected by the presence of antigens (proteins, glycoproteins and others) or by detecting antibodies made against the pathogen

Transgenic animals

Animals whose DNA has been manipulated to possess and express an extra (foreign) gene are called transgenic animals. Transgenic rats, rabbits, pigs, sheep, cows and fish have been produced. More than 95 per cent of all transgenic animals are mice.

Use	Explanation and example
Normal physiology and development	Transgenic animals help to study how genes are regulated and how they affect normal functions of the body and its development. For example, the study of the complex factors such as insulin-like growth factor
Study of disease	Models for human diseases such as cancer, cystic fibrosis, rheumatoid arthritis and Alzheimer's disease help to understand how genes contribute to disease and to develop treatments
Biological products	Medicines are made from transgenic animals. For example, α-1-antitrypsin is used to treat emphysema. Products have been made for phenylketonuria (PKU) and cystic fibrosis
Vaccine safety	Transgenic mice are developed to test the safety of the polio vaccine. If successful and reliable, they could replace the use of monkeys
Chemical safety testing (toxicity testing)	Transgenic animals are made more sensitive to toxic substances than non-transgenic animals. They are exposed to the toxic substances and the effects are studied. This gives results in less time

Rosie the cow. In 1997, Rosie became the first transgenic cow. She produced human protein-enriched milk, about 2.4 grams per litre. The milk contained the human alpha-lactalbumin. It was a nutritionally more balanced product for human babies than natural cow milk.

Ethical issues

Manipulation of living organisms by genetic modification can have unpredictable results when such organisms are put into the ecosystem. So society needs ethical standards to judge the good and the bad of such activity.

The Indian government has set up the Genetic Engineering Approval Committee (GEAC). It makes decisions about the validity of GM research and the safety of introducing GM organisms for public services.

Term	Meaning
Biopiracy	Use of bio-resources by multinational companies and other organisations without proper authorisation from the countries and people concerned, and without paying them compensation
Patent	A right granted by a government to an inventor to prevent others from commercial use of the invention without the inventor's authority

Many companies are attempting to get patents for products and technologies that make use of the genetic materials, plants and other biological resources that have long been identified, developed and used by farmers and indigenous people of a specific region or country. Examples of Indian concern are:

Basmati rice. India grows many varieties of basmati, with distinctive aroma and flavour. In 1997, an American 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 as an "invention". The basmati had been derived from Indian farmer varieties.
Turmeric and neem. Patents on the uses of traditional Indian resources such as turmeric and neem have also raised concern about biopiracy.

The Indian Parliament has cleared the second amendment of the Indian Patents Bill. It has provisions for patent term extension, emergency provisions and research and development initiative.

NEET traps

1. Cry proteins are inactive protoxins in the bacterium. They become active only in the alkaline gut of the insect.
2. cryIAc and cryIIAb control cotton bollworms; cryIAb controls corn borer. Do not mix these up.
3. The Bt toxin kills the insect by creating pores in the midgut epithelial cells, not by acting on the plant.
4. In RNAi, the silencing is of mRNA (translation is blocked); the DNA of the nematode is not cut.
5. The nematode that attacks tobacco roots is Meloidogyne incognita. RNAi works because sense and anti-sense RNAs form dsRNA.
6. Proinsulin contains the C peptide, which is removed. Mature insulin has only the A and B chains.
7. In recombinant insulin production, the A and B chains were made in separate steps and then joined by disulphide bonds.
8. The first gene therapy (1990) was for ADA deficiency and used lymphocytes. It is not a permanent cure unless early embryonic cells are corrected.
9. PCR amplifies nucleic acid; ELISA detects antigens or antibodies. Do not swap them.
10. Rosie the cow produced human alpha-lactalbumin in milk. Over 95 per cent of transgenic animals are mice.

One-liners

1. GM crops can be more tolerant to abiotic stress and need fewer chemical pesticides.
2. Golden rice is enriched with vitamin A.
3. Bacillus thuringiensis makes Cry protein crystals.
4. The Cry protein is converted into its active form by the alkaline pH of the insect gut.
5. cryIAc and cryIIAb act against cotton bollworms; cryIAb acts against corn borer.
6. Meloidogyne incognita is a nematode that attacks tobacco roots.
7. RNAi silences a specific mRNA by a complementary dsRNA.
8. Eli Lilly made human insulin by recombinant DNA technology in 1983.
9. Insulin has an A chain and a B chain joined by disulphide bridges.
10. Proinsulin has an extra C peptide that is removed on maturation.
11. The first clinical gene therapy in 1990 was for ADA deficiency.
12. PCR can detect HIV at an early stage by amplifying its nucleic acid.
13. A mutated gene does not hybridise with the probe, so it is not seen on the film in autoradiography.
14. ELISA works on antigen-antibody interaction.
15. Rosie, the first transgenic cow (1997), gave milk with human alpha-lactalbumin.

Practice questions

The Cry protein used in Bt crops is produced by
1. Thermus aquaticus
2. Bacillus thuringiensis
3. Agrobacterium tumefaciens
4. Bacillus subtilis
Answer
B. Bacillus thuringiensis
Bacillus thuringiensis forms crystals of Cry protein, the Bt toxin.
The gene that gives protection against the corn borer is
1. cryIAb
2. cry gene for nematodes
3. cryIAc
4. cryIIAb
Answer
A. cryIAb
cryIAb controls corn borer; cryIAc and cryIIAb control cotton bollworms.
The inactive Cry protoxin is changed into the active toxin by
1. the enzymes of the plant
2. sunlight on the leaf
3. the acidic pH of the insect gut
4. the alkaline pH of the insect gut
Answer
D. the alkaline pH of the insect gut
The alkaline gut solubilises the crystals and activates the toxin.
The nematode that infects the roots of tobacco plants is
1. Ascaris lumbricoides
2. Bacillus thuringiensis
3. Meloidogyne incognita
4. Wuchereria bancrofti
Answer
C. Meloidogyne incognita
Meloidogyne incognita attacks tobacco roots and lowers the yield.
The A and B chains of insulin are linked together by
1. disulphide bridges
2. hydrogen bonds only
3. glycosidic bonds
4. ionic bonds only
Answer
A. disulphide bridges
The two polypeptide chains are joined by disulphide bridges.
The C peptide is
1. a third chain present in mature insulin
2. the signal that binds insulin to its receptor
3. an extra stretch present in proinsulin that is removed during maturation
4. a part of the A chain
Answer
C. an extra stretch present in proinsulin that is removed during maturation
Proinsulin has the C peptide, which is removed to give mature insulin of A and B chains.
The first clinical gene therapy was given in
1. 1972
2. 1997
3. 1983
4. 1990
Answer
D. 1990
The first gene therapy was given in 1990 to a four-year-old girl with ADA deficiency.
The first clinical gene therapy was used to treat
1. cystic fibrosis
2. adenosine deaminase deficiency
3. adult-onset diabetes
4. phenylketonuria
Answer
B. adenosine deaminase deficiency
ADA deficiency, caused by deletion of the ADA gene, was the first disorder treated.
Rosie, the first transgenic cow, produced milk rich in
1. human alpha-lactalbumin
2. adenosine deaminase
3. human insulin
4. α-1-antitrypsin
Answer
A. human alpha-lactalbumin
Rosie's milk had human alpha-lactalbumin and was more balanced for human babies.
Among all transgenic animals, the percentage that are mice is
1. about 50 per cent
2. more than 95 per cent
3. about 75 per cent
4. about 25 per cent
Answer
B. more than 95 per cent
More than 95 per cent of transgenic animals are mice.
ELISA is based on the principle of
1. amplification of DNA by Taq polymerase
2. hybridisation of a radioactive probe
3. antigen-antibody interaction
4. silencing of mRNA by dsRNA
Answer
C. antigen-antibody interaction
ELISA detects antigens or antibodies against a pathogen.
α-1-antitrypsin made in transgenic animals is used to treat
1. ADA deficiency
2. rheumatoid arthritis
3. adult-onset diabetes
4. emphysema
Answer
D. emphysema
α-1-antitrypsin is used for emphysema.
Biopiracy is
1. the use of bio-resources with a patent granted by the government of the country
2. the testing of GM crops by a government committee
3. the use of bio-resources without proper authorisation and without compensation to the countries and people concerned
4. the study of transgenic animals as disease models
Answer
C. the use of bio-resources without proper authorisation and without compensation to the countries and people concerned
Biopiracy means taking bio-resources without proper authorisation or compensatory payment.
In detecting a mutated gene using a radioactive probe, the clone with the mutated gene does not appear on the photographic film because
1. the probe cannot be tagged with radioactivity
2. the probe is not complementary to the mutated gene
3. the mutated gene destroys the film
4. autoradiography detects only RNA
Answer
B. the probe is not complementary to the mutated gene
The single-stranded probe hybridises only to its complementary sequence.
The two DNA sequences for the insulin chains were introduced by Eli Lilly into plasmids of
1. Salmonella typhimurium
2. Bacillus thuringiensis
3. Agrobacterium tumefaciens
4. Escherichia coli
Answer
D. Escherichia coli
Eli Lilly made the A and B chains in E. coli in 1983.
In India, the validity of GM research and the safety of introducing GM organisms for public services is decided by
1. the Genetic Engineering Approval Committee
2. the farmers of the region
3. a multinational company
4. the Indian Patents Bill
Answer
A. the Genetic Engineering Approval Committee
GEAC makes these decisions.
Given below are two statements: Statement I: Cry proteins exist as inactive protoxins in Bacillus thuringiensis. Statement II: The alkaline pH of the insect gut solubilises the crystals and activates the toxin. Choose the correct answer.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
A. Both Statement I and Statement II are correct
Both statements are correct.
Given below are two statements: Statement I: RNA interference silences a specific mRNA with a complementary double-stranded RNA. Statement II: In RNAi, the DNA of the nematode is cut by the dsRNA. Choose the correct answer.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
C. Statement I is correct but Statement II is incorrect
RNAi silences the mRNA and prevents its translation. It does not cut the DNA.
Given below are two statements: Statement I: Mature human insulin consists of three chains: A, B and C. Statement II: Proinsulin contains the C peptide, which is removed during maturation. Choose the correct answer.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
D. Statement I is incorrect but Statement II is correct
Mature insulin has only A and B chains. Statement II is correct.
Given below are two statements: Statement I: ELISA is based on the hybridisation of nucleic acids. Statement II: PCR is used to detect antigens in a sample. Choose the correct answer.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
B. Both Statement I and Statement II are incorrect
ELISA is based on antigen-antibody interaction and PCR amplifies nucleic acids, so both are incorrect.
Which of the following statements are correct? 1. The first clinical gene therapy in 1990 was for ADA deficiency. 2. Lymphocytes were grown outside the body and given functional ADA cDNA. 3. Gene therapy using lymphocytes is always a permanent cure.
1. 1 and 3 only
2. 2 and 3 only
3. 1 and 2 only
4. 1, 2 and 3
Answer
C. 1 and 2 only
Lymphocytes are not immortal, so periodic infusions are needed and statement 3 is wrong.
Which of the following are uses of transgenic animals? 1. Testing the safety of vaccines 2. Chemical safety (toxicity) testing 3. Studying normal physiology and development
1. 1, 2 and 3
2. 1 and 2 only
3. 2 and 3 only
4. 1 and 3 only
Answer
A. 1, 2 and 3
All three are uses of transgenic animals.
Given below are two statements: Statement I: Most transgenic animals are rabbits. Statement II: Transgenic mice are developed to test the safety of the polio vaccine. Choose the correct answer.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
D. Statement I is incorrect but Statement II is correct
More than 95 per cent are mice, so Statement I is incorrect. Statement II is correct.
Given below are two statements: Statement I: The Genetic Engineering Approval Committee grants patents on bio-resources. Statement II: Biopiracy is the use of bio-resources with proper authorisation. Choose the correct answer.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
B. Both Statement I and Statement II are incorrect
GEAC decides on the validity and safety of GM research. Biopiracy is use without authorisation. Both statements are incorrect.
Given below are two statements: Statement I: Golden rice is enriched with vitamin A. Statement II: The gene cryIAb is used to protect cotton from bollworms. Choose the correct answer.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
C. Statement I is correct but Statement II is incorrect
cryIAb is used against corn borer. Cotton bollworms are controlled by cryIAc and cryIIAb.
Assertion (A): The Bt toxin does not kill Bacillus thuringiensis itself. Reason (R): The toxin exists in the bacterium as an inactive protoxin.
1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true
Answer
A. Both A and R are true and R is the correct explanation of A
The protoxin is activated only in the alkaline gut of the insect.
Assertion (A): Recombinant insulin does not cause allergy to patients. Reason (R): The chains of insulin are linked by disulphide bridges.
1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true
Answer
B. Both A and R are true but R is not the correct explanation of A
The first is true because the insulin is identical to human insulin. The second is also true but does not explain the first.
Assertion (A): Gene therapy using lymphocytes for ADA deficiency is not a permanent cure. Reason (R): The lymphocytes given to the patient are immortal.
1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true
Answer
C. A is true but R is false
The cells are not immortal, so periodic infusions are required.
Assertion (A): Proinsulin consists only of the A and B chains. Reason (R): The C peptide is removed during maturation of proinsulin.
1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true
Answer
D. A is false but R is true
Proinsulin has the extra C peptide, so the assertion is false. The reason is true.
Assertion (A): PCR can detect HIV in the early stage of infection. Reason (R): PCR amplifies the nucleic acid of the virus even when the amount is very low.
1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true
Answer
A. Both A and R are true and R is the correct explanation of A
Amplification makes a very small amount of nucleic acid detectable.
Assertion (A): Transgenic mice are used to test the safety of the polio vaccine. Reason (R): More than 95 per cent of transgenic animals are mice.
1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true
Answer
B. Both A and R are true but R is not the correct explanation of A
Both are true, but the second does not explain the first.
Match List I with List II. List I: a. cryIAc b. cryIAb c. Meloidogyne incognita d. Rosie List II: i. Corn borer ii. Cotton bollworm iii. Human alpha-lactalbumin iv. Nematode of tobacco roots
1. a-ii, b-i, c-iii, d-iv
2. a-i, b-ii, c-iv, d-iii
3. a-ii, b-iv, c-i, d-iii
4. a-ii, b-i, c-iv, d-iii
Answer
D. a-ii, b-i, c-iv, d-iii
cryIAc - cotton bollworm; cryIAb - corn borer; M. incognita - nematode of tobacco roots; Rosie - human alpha-lactalbumin.
Match List I with List II. List I: a. ELISA b. PCR c. Autoradiography with a probe d. Gene therapy List II: i. Amplification of nucleic acid ii. Antigen-antibody interaction iii. Radioactive single-stranded DNA hybridising to its complement iv. Functional gene given to lymphocytes through a retroviral vector
1. a-ii, b-iii, c-i, d-iv
2. a-i, b-ii, c-iii, d-iv
3. a-iii, b-i, c-ii, d-iv
4. a-ii, b-i, c-iii, d-iv
Answer
D. a-ii, b-i, c-iii, d-iv
ELISA - antigen-antibody (ii); PCR - amplification (i); probe - hybridisation (iii); gene therapy - gene to lymphocytes (iv).
Match List I with List II. List I: a. Insulin b. Proinsulin c. ADA deficiency d. Eli Lilly List II: i. Deletion of the enzyme gene ii. Made human insulin in 1983 iii. Contains the C peptide iv. A and B chains joined by disulphide bridges
1. a-iii, b-iv, c-i, d-ii
2. a-iv, b-iii, c-i, d-ii
3. a-i, b-iii, c-iv, d-ii
4. a-iv, b-iii, c-ii, d-i
Answer
B. a-iv, b-iii, c-i, d-ii
Insulin - A and B chains (iv); proinsulin - C peptide (iii); ADA deficiency - gene deletion (i); Eli Lilly - 1983 (ii).
Match List I with List II. List I: a. Normal physiology b. Disease study c. Biological products d. Vaccine safety List II: i. α-1-antitrypsin ii. Polio vaccine tested in mice iii. Effect of insulin-like growth factor iv. Model for Alzheimer's disease
1. a-iv, b-iii, c-i, d-ii
2. a-iii, b-ii, c-i, d-iv
3. a-iii, b-iv, c-i, d-ii
4. a-i, b-iv, c-iii, d-ii
Answer
C. a-iii, b-iv, c-i, d-ii
Physiology - growth factor (iii); disease - Alzheimer's model (iv); products - α-1-antitrypsin (i); vaccine safety - polio vaccine (ii).
Match List I with List II. List I: a. GEAC b. Biopiracy c. Patent d. Basmati rice List II: i. Right to prevent others from commercial use ii. Use of bio-resources without authorisation iii. US patent in 1997 iv. Decides the safety of GM organisms
1. a-i, b-ii, c-iv, d-iii
2. a-iv, b-iii, c-i, d-ii
3. a-ii, b-iv, c-i, d-iii
4. a-iv, b-ii, c-i, d-iii
Answer
D. a-iv, b-ii, c-i, d-iii
GEAC - safety of GM organisms (iv); biopiracy - use without authorisation (ii); patent - right (i); basmati - 1997 US patent (iii).
Match List I with List II. List I: a. Golden rice b. RNAi c. Bt cotton d. Abiotic stress tolerance List II: i. Cry protein ii. Vitamin A enriched iii. Silencing of mRNA iv. Tolerance to cold, drought, salt and heat
1. a-iv, b-iii, c-i, d-ii
2. a-i, b-iii, c-ii, d-iv
3. a-ii, b-iii, c-i, d-iv
4. a-ii, b-i, c-iii, d-iv
Answer
C. a-ii, b-iii, c-i, d-iv
Golden rice - vitamin A (ii); RNAi - silencing (iii); Bt cotton - Cry protein (i); abiotic stress - cold, drought, salt, heat (iv).
Bollworm larvae feeding on a Bt cotton plant die, while the plant remains healthy. This is because
1. the toxin is destroyed in the insect gut
2. the protoxin is activated in the alkaline gut of the larva and makes pores in the midgut cells
3. the plant makes an active toxin that kills the cells of the plant
4. the acidic gut of the larva activates the toxin
Answer
B. the protoxin is activated in the alkaline gut of the larva and makes pores in the midgut cells
Alkaline gut pH activates the Cry protoxin, which creates pores in midgut cells.
A tobacco plant expresses both sense and anti-sense RNA of a nematode gene. The nematode Meloidogyne incognita cannot survive on it because
1. the two RNAs form dsRNA that silences a specific mRNA of the nematode
2. the anti-sense RNA increases translation in the nematode
3. the dsRNA cuts the DNA of the plant
4. the two RNAs make a toxin protein
Answer
A. the two RNAs form dsRNA that silences a specific mRNA of the nematode
The two RNAs pair to form dsRNA, which silences the specific nematode mRNA by RNAi.
A child with ADA deficiency receives genetically engineered lymphocytes but needs the infusion again after some time. This is because
1. the ADA gene is deleted in the donor
2. the retroviral vector destroys the gene
3. the lymphocytes are not immortal
4. enzyme replacement is needed once only
Answer
C. the lymphocytes are not immortal
The cells have a limited life, so periodic infusions are needed unless early embryonic cells are corrected.
A clinic needs to detect a very small amount of HIV nucleic acid in a patient's sample at an early stage. The most suitable technique is
1. blood grouping
2. PCR
3. serum analysis alone
4. urine analysis
Answer
B. PCR
PCR amplifies the nucleic acid, so a low amount can be detected.
A company wants to test the toxicity of a chemical quickly. It uses animals that are more sensitive to toxic substances than normal animals. These are
1. transgenic animals, which give results in less time
2. non-transgenic animals, which give results in less time
3. transgenic plants, which give results in less time
4. non-transgenic animals, which are more sensitive
Answer
A. transgenic animals, which give results in less time
Transgenic animals are made more sensitive to toxic substances, so results come sooner.
After the A and B chains of insulin are made in separate E. coli cultures and extracted, they must be
1. treated with the alkaline gut juice
2. joined with the C peptide
3. cut by restriction enzymes
4. joined by creating disulphide bonds
Answer
D. joined by creating disulphide bonds
The chains are combined by disulphide bonds to give human insulin.
A radioactive single-stranded probe is hybridised to cloned cells and detected by autoradiography. One clone gives no signal. The likely reason is that this clone
1. has no DNA at all
2. carries the normal gene complementary to the probe
3. has high levels of antigens
4. carries a mutated gene not complementary to the probe
Answer
D. carries a mutated gene not complementary to the probe
A mutated sequence is not complementary to the probe, so it does not hybridise and gives no signal.

Page 1 of 1

Finished reading?

Test yourself in 10 minutes

A free 10-question mini-mock on your exam's real pattern, with negative marking and an instant score. अपनी तैयारी 10 मिनट में जाँचें।

Take a free mini-mock →Topic-wise practice