NCERT Exemplar Solutions for Class 12 Biology chapter 12 Biotechnology and Its Applications
These Solutions are part of NCERT Exemplar Solutions for Class 12 Biology. Here we have given NCERT Exemplar Solutions for Class 12 Biology chapter 12 Biotechnology and Its Applications
Multiple Choice Questions
Bt cotton is not
(a) a GM plant
(b) insect resistant
(c) a bacterial gene expressing system
(d) resistant to all pesticides.
(d) : Several transgenic plants have been developed. One such plant is Bt cotton in which the Bt toxin from the bacterium Bacillus thuringiensis has been used as a biological insecticide. The choice of genes depends upon the crop and targeted pest. Bt cotton is resistant to insects but is not pesticide resistant.
C-peptide of human insulin is
(a) a part of mature insulin molecule
(b) responsible for formation of disulphide bridges
(c) removed during maturation of pro-insulin to insulin
(d) responsible for its biological activity.
(c) : In mammals, including humans, insulin is synthesized as a pro-hormone which needs to be processed before it becomes a fully mature and functional hormone. It contains an extra, stretch called the C peptide which is removed during maturation into insulin.
GEAC stands for
(a) Genome Engineering Action Committee
(b) Ground Environment Action Committee
(c) Genetic Engineering Approval Committee
(d) Genetic and Environment Approval Committee.
(c) : Genetic modification of organisms can have unpredictable results when such organisms are introduced into the ecosystem. Therefore, the Indian Government has set up organizations such as GEAC (Genetic Engineering Approval Committee), which makes decisions regarding the validity of GM research and the safety of introducing GM- organisms for public services.
a-1 antitrypsin is
(a) an antacid
(b) an enzyme
(c) used to treat arthritis
(d) used to treat emphysema.
(d) : Disorders of a-l-antitrypsin protein include a-l-antitrypsin deficiency, an autosomal, codominant hereditary disorder in which deficiency of a-l-antitrypsin leads to a chronic uninhibited tissue breakdown. This causes the degradation of lung tissue, and eventually leads to characteristic manifestations of pulmonary emphysema.
A probe which is a molecule used to locate specific sequences in a mixture of DNA or RNA molecules could be
(a) a single stranded RNA
(b) a single stranded DNA
(c) either RNA or DNA
(d) can be ss DNA but not ss RNA.
(a, b) : The molecular probes are usually single stranded pieces of DNAs (sometimes RNAs) labelled with radio isotopes such phosphorus-32. Molecular probes are available for many genetic disorders such as Duchenne muscular dystrophy, cystic fibrosis, Tay-Sachs disease.
Choose the correct option regarding retrovirus.
(a) An RNA virus that can synthesise DNA during infection.
(b) A DNA virus that can synthesise RNA during infection.
(c) A ssDNA virus.
(d) A dsRNA virus.
(a) : A retrovirus is a ssRNA virus that stores its nucleic acid in the form of an mRNA genome and targets a host cell as an obligate parasite. Once inside the host cell cytoplasm, the virus uses its own reverse transcriptase enzyme to produce DNA from its RNA genome (the reverse of usual pattern, thus retro).
The site of production of ADA in the body is
(c) blood plasma
(b) : Lymphocytes are a kind of white blood cells present in bone marrow. ADA (adenosine deaminase) is an enzyme that is present in lymphocytes and is very important for the immune system to function.
A protoxin is
(a) a primitive toxin
(b) a denatured toxin
(c) toxin produced by protozoa
(d) inactive toxin.
Pathophysiology is the
(a) study of physiology of pathogen
(b) study of normal physiology of host
(c) study of altered physiology of host
(d) none of the above.
(c) : Pathophysiology means the functional changes in the affected person associated with or resulting from a disease or injury or a syndrome.
The trigger for activation of toxin of Bacillus thuringiensis is
(a) acidic pH of stomach
(b) high temperature
(c) alkaline pH of gut
(d) mechanical action in the insect gut.
(c) : The Bt toxin proteins exist as inactive protoxins but once an insect ingests the inactive toxin it is converted into an active form of toxin due to the alkaline pH of the
alimentary canal that solubilises the crystals. The activated toxin binds to the surface of midgut epithelial cells and create pores which causes cell swelling and lysis and finally cause death of the insect.
Golden rice is
(a) a variety of rice grown along the yellow river in China
(b) long stored rice having yellow colour tint
(c) a transgenic rice having gene for (3-carotene)
(d) wild variety of rice with yellow coloured grains.
(c) : Golden rice is a transgenic variety of rice (Oryza sativa) which contains good quantities of (3-carotene (provitamin A- inactive state of vitamin A). (3-carotene is a principle source of vitamin A. Since the grains (seeds) of the rice are yellow in colour due to (3-carotene, the rice is commonly called golden rice.
In RNAi, genes are silenced using
(c) : RNAi takes place in all eukaryotic organisms as a method of cellular defense. This method involves silencing of a specific mRNA due to a complementary dsRNA molecule that binds to and prevents translation of the mRN A (silencing). 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.
The first clinical gene therapy was done for the treatment of
(c) cystic fibrosis
(d) SCID (Severe Combined Immuno Defici-ency resulting form deficiency of ADA).
(d) : 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. ADA deficiency can lead to Severe Combined Immuno Deficiency (SCID).
ADA is an enzyme which is deficient in a genetic disorder SCID. What is the full form of ADA?
(a) Adenosine deoxyaminase
(b) Adenosine deaminase
(c) Aspartate deaminase
(d) Arginine deaminase
(b) Refer answer 13.
Silencing of a gene could be achieved through the use of
(a) RNAi only
(b) antisense RNA only
(c) both RNAi and antisense RNA
(d) none of the above.
(c) : For RNAi refer answer 12.
Antisense RNA is an RNA molecule whose base sequence is complementary to that of the sense RNA. It can undergo base pairing with its comlementary mRNA and block the gene expression either by preventing access for ribosomes to translate the mRNA or by triggering degradation of the dsRNA by ribonucleases. Flavr savr variety of tomato is produced using this antisense technology in which an artificial gene inserted for antisense RNA prevented expression of genes that cause ripening. It has been found that RNA interference is more effective than antisense RNA.
Very Short Answer Type Questions
In view of the current food crisis, it is said, that we need another Green Revolution. Highlight the major limitations of the earlier Green Revolution.
BID Limitations of Green Revolution are:
- Increased crop yield is not sufficient to feed the increasing human population.
- Fertilisers and pesticides which are used to increase the food production are not good for environment.
- Green revolution was agrochemical based, and as agrochemicals are expensive so, small farmers cannot afford them.
Expand GMO. How is it different from a hybrid?
GMO is Genetically Modified Organism.
Differences between GMO and hybrid are as follows:
|(1) GMO is obtained by inserting foreign gene into an organism.
|Hybrid is produced by crossing two superior individuals
|(2) Change in genotype is precisely controlled.
|Change in genotype depends on chance segregation or aggregation during fertilisation.
|(3) New traits are introduced
|Existing traits of parents are reshuffled.
Differentiate between diagnostics and therapeutics. Give one example and for each category.
Diagnosis refers to the detection of disease and understanding its pathophysiology (symptoms, causes etc.) so that it can be cured. It involves ELISA, PCR, blood tests etc. Whereas, therapeutics is treatment of disease by providing proper medication or replacing defective genes by normal ones. E.g., Vaccines, production of humulin, antibiotics etc.
Give the full form of ELISA. Which disease can be detected using it? Discuss the principle underlying the test.
HELISA is Enzyme Linked Immuno- sorbant Assay. ELISA is used for detecting HIV, Hepatitis-B virus etc. diseases. ELISA f is based on principle of antigen-antibody interaction. An antibody (Ab) reacts with the concerned antigen (Ag) in a highly specific manner and forms Ag-Ab complex. A second antibody conjugated with enzyme specific to a second site on the test protein is added. The enzyme causes colour change and this colour change is analysed to identify the condition.
Can a disease be detected before its symptoms appear? Explain the principle involved.
Yes, a disease can be detected when symptoms are not yet visible due to very low
coqnt of pathogens, by the technique called Polymerase Chain Reaction (PCR). PCR multiplies pathogen nucleic acids and by analysing them, disease can be diagnosed. By PCR, even very low amounts of DNA can be detected and amplified. It is used to detect HIV and many other genetic disorders etc.
Write a short note on biopiracy highlighting the exploitation of developing countries by the developed countries.
Biopiracy is exploitation of bioresources of a country by organisations and multi-nationals for commercial exploitation with or without patent but without any Access and Benefit Sharing Agreement (ABA). Bioresources or biological resources are all those organisms which can provide commercial benefits. They are abundant in developing countries which are poor in technology though the countries have traditional knowledge related to bioresources. On the other hand, developed countries are poor in bioresources but are rich in technology. Traditional knowledge helps in saving time, effort and expenditure in developing refined product for commercialisation. Therefore, based on traditional knowledge, institutions and companies of industrialised nations are collecting and exploiting bioresources of other nations by getting them patented.
Many proteins are secreted in their inactive form. This is also true of many toxic proteins produced by microorganisms. Explain how the mechanism is useful for the organism producing the toxin?
Bacillus thuringiensis is one such organism which produces a toxic protein in its inactivated form (protoxin). The benefit of doing so is that the bacterium itself remains unaffected from the toxic effects but once an insect ingests it, the alkaline pH of insect’s gut changes it into active form. The activated toxin binds to the surface of midgut epithelial cells and creates pores which cause cell swelling and lysis and death of an insect, but the bacterium remains unaffected.
While creating genetically modified organisms, genetic barriers are not respected. How can this be dangerous in the long run?
Genetically modified organisms can be dangerous in long run due to following reasons :
- It is possible that insects might become resistant to Bt or other crops that have been genetically modified to produce their own pesticides.
- Genetically engineered herbicide crop plants and weeds may cross breed, resulting in transfer of herbicide resistance genes from crops into weeds. Therefore, weeds would also be herbicide tolerant.
- The enzyme produced by antibiotic resistance gene can cause allergies, because it is a foreign protein.
- Genetically engineered microbes may be uncontrollable if get released in ecosystems. They may also transfer virulence to other microbial populations.
- GMOs can be dangerous to other organisms in the ecosystem. Such as honeybees show toxicity to pollens of insect resistant crops.
Why has the Indian Parliament cleared the second amendment of the country’s patents bill?
The Indian Parliament has recently also cleared second amendment of the Indian Patents Bill because there has been growing realisation of injustice, inadequate compensation and benefit sharing between developed and developing countries. Such patent bills prevent unauthorised exploitation of bioresources and traditional knowledge of a country and consider emergency provisions and development initiative.
Give any two reasons why the patent on basmati should not have gone to an American Company.
Patents on basmati should not have gone to an American Company because:
- Presence of rice goes back thousands of years in Asia’s agricultural history. There are over 2,00,000 varieties of rice in India alone.
- The “new” variety of basmati having the US patent had actually been derived from Indian farmer’s varieties by crossing Indian basmati with semi-dwarf varieties.
How was insulin obtained before the advent of rDNA technology? What were the problems encountered?
Before the advent of rDNA technology, insulin was extracted from pancreas of slaughtered pigs and cattle, as insulin is secreted by (3-cells of islets of Langerhans of pancreas. Problem encountered was that this insulin was different from human insulin and caused some undiserable side effects such as allergy.
With respect to understanding diseases, discuss the importance of transgenic animal models.
Animals having foreign gene inserted in their genome by rDNA technology are called transgenic animals. Many transgenic animals have been developed to increase our understanding of how genes contribute to the development of disease so that investigation of new treatments for diseases is made possible. Now transgenic models exist for many human diseases such as cancer, cystic fibrosis, rheumatoid arthritis, Alzheimer’s disease, haemophilia, thalessaemia, etc. Such transgenic animals have been created which code for particular products of therapeutic value such as human protein (a-l-antitrypsin) which is used to treat emphysema (sheep), tissue plasmogen activator (goat), blood clotting factors VIII and IX (sheep) and lactoferrin (cow).
Name the first transgenic cow. Which gene was introduced in this cow?
First transgenic cow was ‘Rosie’. The gene introduced was the gene for human a lactalbumin. It resulted in production of a lactalbumin (human protein) rich milk which is for more nutritious than normal milk.
PCR is a useful tool for early diagnosis of an infectious disease. Elaborate.
Early detection of disease refers to diagnosis before the symptoms are seen. In this case, pathogen (bacteria or virus) are present in very less number, i.e., not capable of producing visible symptoms. Here, PCR is used to multiply their genetic material to get enough quantities to be analysed. E.g., it is used to detect HIV virus in AIDS patient, gene mutations in suspected cancer patients, etc.
What is GEAC and what are its objectives?
GEAC is Genetic Engineering Approval Committee, which has been set up by Indian government.
Objectives of GEAC are as follows:
- To ensure safety of Genetically Modified Organisms (GMO) for public services, i. c., safely using GM organisms for food, medicine etc.
- To take decisions regarding validity of GM research.
For which variety of Indian rice, the patent was filed by USA company?
USA company got patent rights on basmati rice of India. They claimed to develop “new” variety by crossing basmati rice with semi-dwarf varieties.
Discuss the advantages of GMO.
USAdvantages of Genetically Modified Organisms (GMO) are:
- GM crops are more tolerant to abiotic stresses.
- They are disease resistant.
- GM plants have increased nutritional value.
- Transgenic mice are being used for testing vaccine safety.
- Transgenic animals have been used + as model for studying many human diseases.
Short Answer Type Questions
Gene expression can be controlled with the help of RNA. Explain the method with an example.
Silencing of gene expression using a dsRNA is called RNA interference (RNAi). It involves silencing of specific mRNA due to complementary dsRNA molecule that binds to and prevent translation of n;RNA. Using Agrobacterium vectors, nematode specific genes have been introduced into the host plant (tobacco plant). The introduction of DNA was such that it produced both sense and anti¬sense RNA in the host cells. These two RNAs being complementary to each other formed a dsRNA (double stranded RNA) that initiated RNAi.
Different steps involved in making tobacco plant resistant to nematode are briefly described below:
- RNase enzyme called ‘dicer’ cuts all dsRNA molecules into small interfering RNAs (siRNAs) (21-23 nucleotides long).
- Each siRN A complexes with ribonucleases (distinct from dicer) to form an RNA- induced silencing complex (RISC).
- The siRNA unwinds and RISC is activated.
- 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 wRNA. This destroys the 77! RNA.
- When 77/RNA of the parasite is destroyed no parasite proteins are synthesised. It results in the death of the parasite (nematode) in the transgenic host. Thus the transgenic plant gets itself protected from the parasite.
Ignoring our traditional knowledge can prove costly in the area of biological patenting. Justify.
Ignoring traditional knowledge is harmful for developing countries as developed nations take advantage of this. Developing nations are rich in traditional knowledge and biodiversity but are poor in finances and thus are not able to exploit modern applications for commercialisation of bioresources. E.g., basmati rice of India was patented by US company which was later challenged by Indian government.
Highlight any four areas where genetic modification of plants has been useful.
Four areas where genetic modification of plants has been successful are :
- Tolerance of abiotic stress like drought and salinity.
- Better nutritional value.
- Increased efficiency of mineral utilisation.
- Reduced post harvest losses.
What is a recombinant DNA vaccine? Give two examples.
Recombinant DNA vaccines are vaccines that are produced by genetic modification technique. For production of such vaccines, microbes are programmed to produce desired antigenic fragment. E.g., vaccine against hepatitis B virus consists of a portion of the viral protein coat produced by genetically modified yeast.
Why is it that the line of treatment for a genetic disease is different from infectious diseases?
Infectious diseases are due to infection with a pathogen. They are treated by killing or inhibiting the growth of pathogen by taking various drugs or by strengthening our immune system. Genetic disorders are due to defect in genes, and subsequent defective protein and enzyme formation and subsequent can be cured by gene therapy, which involves replacement of faulty genes by healthy genes.
Discuss briefly how a probe is used in molecular diagnostics.
The molecular probes are usually pieces of ssDNA (or RNA) labelled with radio isotopes such as 32P. These are used for molecular diagnosis of various diseases such as Duchenne muscular dystrophy, cystic fibrosis, Tay-Sachs disease etc.
In molecular diagnosis, a single stranded DNA or RNA joined with a radioactive molecule (probe) is allowed to hybridise with its complementary strand followed by detection using autoradiography.
Who was the first patient who was given gene therapy? Why was the given treatment recurrent in nature?
The first clinical gene therapy was given in 1990 to a 4 – year old girl named Ashanti de Silva with adenosine deaminase (ADA) deficiency. This enzyme is very important for the immune system to function as its deficiency causes SCID. In some children, ADA deficiency can be cured by bone marrow transplantation. However, in others it can be treated by enzyme replacement therapy, in which functional ADA is given to the patient by injection. But in both approaches the patients are not completely cured.
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 a permanent cure.
Taking examples under each category, discuss upstream and downstream processing.
A biotechnological manufacturing process can be separated into upstream processes and downstream processes. Upstream processing refers to the entire process of selecting and isolating cells to be used, their cultivation, cell banking and culture expansion of the cells until final harvest (termination of the culture and collection of the live cell batch) is achieved. For example, in production of humulin, upstream processing includes cell line preparation by obtaining human insulin gene, and inserting it into E. coli cells and media and equipment preparation.
Downstream processing is the part where the final harvest is purified and quality checked to make it suitable for commercial applications. Suitable preservatives may also be added. For example, in production of humulin, downstream processing includes lysis of the bacterial cells, separation of cell components from the products, synthesis of active insulin by joining A and B chains to produce mature insulin and its purification to obtain highly purified insulin, fit for medicinal use.
Antigens (Ag) are substances which when introduced into the body, stimulate the production of antibodies. Antibodies (Ab) are immunoglobulins which are produced in the body in response to antigens or foreign bodies.
Two diagnostic kits based on Ag and Ab are :
- ELISA which is used for detection of diseases like HIV.
- Pregnancy test kit.
ELISA technique is based on the principles of antigen-antibody interaction. Can this technique be used in the molecular diagnosis of a genetic disorder, such as phenylketonuria?
Yes, ELISA can be used in diagnosis of a genetic disorder, such as phenylketonuria. In this process antibody against the enzyme which is responsible for the metabolism of phenylalanine i.e. phenylalanine hydroxylase, is used to develop the ELISA based diagnostic technique. The patient has deficiency of this enzyme, thus will test negative while a normal individual which has this enzyme in its body, will test positive.
How is a mature, functional insulin hormone different from its prohormone form?
The mature insulin consists of two polypeptide chains – chain A and chain B. The pro-hormone insulin contains an extra C-peptide which is removed during maturation and is not present in mature insulin hormone.
Gene therapy is an attempt to correct a genetic defect by providing a normal gene into the individual. By this, the normal function can be restored. An alternate method would be to provide the gene product (protein/enzyme) known as enzyme replacement therapy, which would also restore the function. Which in your opinion is a better option? Give reason for your answer.
Gene therapy is better to cure genetic defect than enzyme replacement therapy because in enzyme replacement therapy a functional ADA is given to the patient by injection and patients do not have functional T-lymphocytes to provide immune response against pathogens and thus patient is not completely cured. In gene therapy, the isolated gene from bone marrow cells producing ADA can be introduced into cells at early embryonic stages and therefore can provide permanent cure.
Transgenic animals are the animals in which a foreign gene is expressed. Such animals can be used to study the fundamental biological process, phenomenon as well as for producing products useful for mankind. Give one example for each type.
Transgenic animals used to study fundamental biological processes include transgenic mice in which some specific genes are deleted or replaced with nonfunctional genes thought to be associated with fundamental processes like ageing. Then, the effect of this gene’s absence is studied.
A transgenic animal used to produce products useful for mankind may be exemplified by rosie, a transgenic cow that has gene for human lactalbumin inserted in its genome which is expressed in its milk making it more nutritious.
When a foreign DNA is introduced into an organism, how is it maintained in the host and how is it transferred to the progeny of the organism?
The foreign genes are inserted into the genome of an organism using recombinant DNA technology to produce a transgenic organism. This foreign gene is maintained in the host organism because as its cells undergo division, rDNA also gets replicated alongwith the cell chromosomes and daughter cells receive copies of rDNA. Similarly, during reproduction, reproductive cells get the rDNA along ,with the other chromosomes and as a result, the transgenic trait is transferred to the progeny. Chances are 100%, if the organism reproduces asexually.
Bt cotton is resistant to pests, such as iepidopteran, dipterans and coleopterans. is Bt cotton also resistant to other pests as well?
Bt cotton is made resistant against specific pests only. Soil bacterium Bacillus thuringiensis produces proteins that kills certain insects like lepidopterans (tobacco budworm), coleopterans (beetles) and dipterans (flies) etc. It does not have gene which is effective against all type of insect pests. Therefore, other pests may attack cotton plant.
Long Answer Type Questions
A patient is suffering from ADA deficiency. Can he be cured? How?
Gene therapy is the technique of genetic engineering used to replace 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. Severe combined immunodeficiency (SCID) is caused due to defect in the gene for the enzyme adenosine deaminase. SCID patient lacks functional T-lymphocytes and, therefore, fails to fight the infecting pathogens.
To perform gene therapy, lymphocytes are extracted from the patient’s bone marrow and a normal functional copy of human gene coding for ADA is introduced into these lymphocytes with the help of retroviral vector. The cells so treated are reintroduced into the patient’s bone marrow. The lymphocytes produced by these cells contain functional ADA gene which reactivates the victim’s immune system.
But, as these lymphocytes do not divide and are short lived, so periodic infusion of genetically engineered lymphocytes is required. This problem can be overcome, if stem cells are modified at early embryonic stage.
Define transgenic animals. Explain in detail any four areas where they can be utilised.
The organisms which have their DNA manipulated to possess and express a foreign or extra gene are known as transgenic animals. Various areas where transgenic animals can be used are as follows:
- Transgenic animals produce useful products, such as human protein (a-1- antitrypsin) used to treat emphysema. Attempts are being made for treatment of phenylketonuria and cystic fibrosis.
- Transgenic mice are being used for testing the safety of vaccines before they are used for human beings. E.g., they are being used to test the safety of polio vaccine.
- Transgenic animals act as models for human diseases like cancer, cystic fibrosis, rheumatoid arthritis, Alzheimer’s disease etc., and their possible new methods of their treatment.
- Transgenic animals are specifically developed to study, how genes are regulated and how they affect normal functioning of the body and its development. E.g. study of complex factors involved in growth, such as insulin like growth-factor (IGF).
You have identified a useful gene in bacteria. Make a flow chart of the steps that you would follow to transfer this gene to a plant.
Highlight five areas where biotechnology has influenced our lives.
Various areas where biotechnology has influenced our lives are :
- Gene therapy – A collection of methods that allows correction of a gene defect diagnosed in a person, child or an embryo.
- Molecular diagnosis – Early detection and treatment of diseases before their symptoms start appearing.
- Production of proteins using rDNA technique – Several proteins have been produced in abundance for curing certain diseases. They include insulin, growth hormone, interferons, vaccines etc.
- Agricultural applications – rDNA technology has developed transgenic plants which can tolerate drought, various diseases and have increased productivity.
- Industrial applications – Enzymes are synthesised and used to produce sugar, cheese and detergents etc.
What are the various advantages of using genetically modified plants to increase the overall yield of the crop?
Advantages of genetically modified plants are as follows :
- Tolerance – GM plants are resistant to abiotic stresses (drought, cold, salinity, heat).
- Pest resistance – GM plants are pest resistant and can reduce the utilisation of chemical insecticides or pesticides e.g. Bt cotton.
- Disease resistance – Genetically modified plants are resistant to various diseases caused by bacteria, virus, fungus etc.
- Reduced post harvest losses – GM plants have helped to reduce post harvest losses, e.g. flavr savr transgenic tomatoes.
- Increased efficiency of mineral usage – GM plants can more efficiently utilise soil minerals and thus prevent early exhaustion of fertility of soil.
- Increased nutritional value of food – GM plants have enhanced nutritional value of food, e.g. golden rice is rich in vitamin A.
Explain with the help of one example how genetically modified plants can
(a) reduce usage of chemical pesticides.
(b) enhance nutritional value of food crops.
(a) GM crops are pest resistant crops. E.g., a nematode Meloidogyne incognita infects the roots of tobacco plant and causes lots of damage by reducing the yield. Using Agrobacterium vectors nematode specific genes are introduced into the host plant, as a result they produce both sense and antisense RNA. This initiates RNAi i.e. a specific segment of RNA is made silent and is unable to produce the protein required by the nematode. The nematode dies in such a transgenic host. By this way, using biotechnological technique the transgenic plant gets protected by itself without using chemical pesticides,
(b) GM plants have increased nutritional vdlue of food. E.g., golden rice is a transgenic variety of rice, which contains good quantities of (3 carotene (provitamin A). Since the contents of vitamin A are very low in rice, so genetically engineered rice have been produced by introducing three genes associated with synthesis of carotene. The grains of transgenic rice are rich in provitamin and reduce the occurrence of vitamin A deficiency diseases.
List the disadvantages of insulin obtained from the pancreas of slaughtered cows and pigs.
Disadvantages of insulin obtained from slaughtered cows and pigs are as follows :
- As insulin from slaughtered animals is produced in vary small amounts, so it requires killing of large number of animals.
- Insulin produced by animals is slightly different from human insulin, therefore it sometimes does not respond well and causes allergy.
- It is unethical to kill so many animals to obtain a drug.
- Due to infection by microorganisms, some animals might produce contaminated insulin.
- Its production is a more time taking process and the supply is also limited.
List the advantages of recombinant insulin.
Advantages of recombinant insulin are as follows:
- Recombinant insulin exactly resembles human insulin in structure and is commonly called humulin.
- It is available in pure form, therefore, chances of contamination are very little.
- Its production does not involve killing of animals.
- There is no immune response or allergy or any other side effects.
- There is no shortage of supply.
What is meant by the term biopesticide? Name and explain the mode of action of a popular biopesticide.
A biopesticide is a living organism and not a chemical substance. Its product or gene can kill the pest, thus it is used for pest control and is thus named so. It is highly specific and safe for the environment. It does not cause any pollution in the environment. Bt toxin is a biopesticide produced from Bacillus thuringiensis.
Bt toxins are proteins that kill certain insects like lepidopterans, coleopterans and dipterans. This protein exists in inactive form in bacteria and does not cause any harm to it. Once an insect ingests the inactive toxin, it gets converted into active form of toxin due to alkaline pH of alimentary canal of the insect, that solubilises the crystals.
The activated toxin binds to the surface of the midgut epi thelial cells of the insect and create pores which cause swelling and lysis and finally the death of insect. Bt toxin crystals are used as pesticide in agriculture. The protein crystals are available commercially as liquids which are sprayed on the leaves. When a insect pest ingests them, the toxins get inactivated inside the insect and kill it. With advances in the field of biotechnology, genetic engineering techniques have been used to incorporate pest resistance in crop plants. The Bt toxin genes are isolated from Bacillus thuringiensis and incorporated into several crop plants like cotton. Bt cotton farming has shown good results in various parts of the country.
Name the five key tools for accomplishing the tasks of recombinant DNA technology. Also mention the functions of each tool.
Five key tools for recombinant DNA technology are :
- Cleaving enzymes – Restriction endonucleases cleave DNA at specific points and exonucleases cut DNA at the terminal end.
- DNA ligase – Enzyme used for sealing gaps in DNA fragment and for joining foreign gene with plasmid DNA.
- Vectors – Vectors are DNA molecule that carry foreign DNA segment and replicate inside host cell, e.g., plasmid.
- Competent host – Cell capable of transformation, i.e., able to take foreign DNA.
- Eysing enzymes – To open the cell to isolate the DNA.
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