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UNIT VI REPRODUCTION
Chapter 1 : Sexual Reproduction in Flowering Plants
Chapter 2 : Human Reproduction
Chapter 3: Reproductive Health
UNIT VII GENETICS AND EVOLUTION
Chapter 4 : Principles of Inheritance and Variation
Chapter 5: Molecular Basis of Inheritance
UNIT VIII BIOLOGY IN HUMAN WELFARE
Chapter 7 : Human Health and Disease
Chapter 8: Microbes in Human Welfare
UNIT IX BIOTECHNOLOGY
Chapter 9 : Biotechnology : Principles and Processes
Chapter 10 : Biotechnology and its Applications
UNIT X ECOLOGY
Biotechnology has many applications such as biopharmaceuticals, therapeutics, diagnostics, genetically modified crops, processed food, bioremediation, waste treatment and energy production.
Biotechnology has 3 critical research areas:
a. Providing the best catalyst in the form of improved organism usually a microbe or enzyme.
b. Creating optimal conditions through engineering for a catalyst to act.
c. Downstream processing technologies to purify the protein/organic compound.
APPLICATIONS IN AGRICULTURE
3 options for increasing food production:
a. Agro-chemical based agriculture: It uses fertilizers & pesticides. Expensive. Causes environmental pollution.
b. Organic agriculture: Expensive.
c. Genetically engineered crop-based agriculture: It uses genetically modified crops. Genetically Modified Organisms (GMO) are the plants, bacteria, fungi & animals whose genes are altered by manipulation.
Advantages of genetic modification in plants:
• It makes crops more tolerant to abiotic stresses (cold, drought, salt, heat etc.).
• Pest-resistant crops reduce the use of chemical pesticides.
• It reduces post-harvest losses.
• It increases efficiency of mineral usage by plants (it prevents early exhaustion of soil fertility).
• It enhances nutritional value of food. E.g. Golden rice (Vitamin A enriched rice).
• To create tailor-made plants to supply alternative resources (starches, fuels, pharmaceuticals etc.) to industries.
Pest Resistant Plants
- They act as bio-pesticide.
- It reduces the need for insecticides.
- E.g. Bt cotton, Bt corn, rice, tomato, potato, soyabean etc.
Bt Cotton: -
Some strains of Bacillus thuringiensis have proteins that kill insects like coleopterans (beetles), lepidopterans (tobacco budworm, armyworm) & dipterans (flies, mosquitoes).
- B. thuringiensis forms an insecticidal protein (Bt toxin) crystal during a phase of their growth. It does not kill theBacillus as it exists as inactive protoxins.
- When an insect ingests the toxin, it becomes active due to alkaline pH of the gut which solubilise the crystals. Toxin binds to surface of mid-gut epithelial cells creating pores. It causes cell swelling and lysis and death of the insect.
- Bt toxin genes were isolated from B. thuringiensis and incorporated into crop plants such as cotton.
- Most Bt toxins are insect-group specific. They are coded by cry genes. E.g. proteins encoded by cryIAc & cryIIAb genes control cotton bollworms. Protein of cryIAb gene controls corn borer.
Nematode resistance in tobacco plants: -
A nematode Meloidogyne incognita infects the roots of tobacco plants causing a reduction in yield.
- It can be prevented by RNA interference (RNAi) strategy. - RNAi is a method of cellular defense in all eukaryotic organisms. It prevents translation of a specific mRNA (silencing) due to a complementary dsRNA molecule.
- The source of this complementary RNA is from an infection by RNA viruses or mobile genetic elements (transposons) that replicate via an RNA intermediate.
- Isolate Nematode-specific genes (DNA). It is introduced into host plant using Agrobacterium vectors. It produces both sense & anti-sense RNA in host cells. These RNAs are complementary. So they form double stranded (ds) RNA. It initiates RNAi and silences the specific mRNA of nematode. Thus the parasite cannot survive in a transgenic host expressing specific interfering RNA.
APPLICATIONS IN MEDICINE
- Recombinant DNA technology helps for mass production of safe and more effective therapeutic drugs.
- Products from non-human sources cause unwanted immunological responses. But recombinant therapeutics does not have such problems.
- At present, about 30 recombinant therapeutics have been approved. Of these, 12 are being marketed in India.
1. Genetically Engineered Insulin
- Insulin is used to manage adult-onset diabetes.
- Insulin from the pancreas of animals (cattle & pigs) causes allergy or other types of reactions to the foreign protein.
- Now, it is possible to produce human insulin using bacteria.
- Insulin consists of two short polypeptide chains (chain A & chain B) that are linked by disulphide bridges
- In mammals, insulin is synthesized as a pro-hormone (pro-insulin). It is processed to become mature and functional hormone.
- The pro-hormone contains an extra stretch called C peptide. This is removed during maturation into insulin.
- In 1983, Eli Lilly (an American company) prepared two DNA sequences corresponding to A & B chains of human insulin and introduced them in plasmids of E. coli to produce insulin chains. Chains A & B were combined by creating disulfide bonds to form human insulin (Humulin).
As students will recall from the previous chapter, biotechnology is concerned with the industrial-scale production of biopharmaceuticals and biologicals using genetically modified microbes, fungi, plants, and animals. Therapeutics, diagnostics, genetically modified crops for agriculture, processed food, bioremediation, waste treatment, and energy production are all examples of biotechnology applications. Biotechnological Applications in Agriculture, Biotechnological Applications in Medicine, Transgenic Animals, and Ethical Issues are also covered in this chapter. Application of biotechnology in health and agriculture: human insulin and vaccine production, stem cell technology, gene therapy; genetically modified organisms - Bt crops; transgenic animals; biosafety issues, biopiracy, and patents are covered.
1. Crystals of Bt toxin produced by some bacteria do not kill the bacteria themselves because –
(a) bacteria are resistant to the toxin
(b) toxin is immature;
(c) toxin is inactive;
(d) bacteria encloses toxin in a special sac.
Solution:
(c) toxin is inactive
Toxins in bacteria are found in an inactive form known as prototoxin. This gets converted into an active form when it moves into the body of an insect.
2. What are transgenic bacteria? Illustrate using any one example.
Solution:
Transgenic bacteria comprise of a foreign gene which is purposefully inserted into its genome. These are manipulated in order to be able to express the favorable gene to produce different commercially important products.
E.coli, an example of transgenic bacteria has two DNA sequences in its plasmid that corresponds to A and B chain of human insulin which are introduced to generate the respective human insulin chains. Therefore, once the insulin gene is introduced into the bacterium, it turns transgenic and begins to produce chains of human insulin. These chains, after sometime are extracted from E.coli and fused to form human insulin.
3. Compare and contrast the advantages and disadvantages of production of genetically modified crops.
Solution:
Advantages of producing genetically modified crops are:
• Genetic modification makes crops more tolerant to abiotic stresses – namely cold, drought, heat, salt etc
• Genetic modification creates tailor-made plants to supply alternative resources to industries, in the form of fuels, starches, pharmaceuticals etc
• Most of the crops produced this way are for pest resistance, that increases crop productivity and hence reduces the dependence on chemical pesticides
• Genetic modification has made it possible to develop crops that enhance the nutritional quality. For instance, one of the transgenic variety of rice, golden rice, is rich in Vitamin A.
• They are useful in reducing the losses that are incurred post-harvest
• Early exhaustion of soil fertility is prevented due to increased productivity of mineral usage by plants
Disadvantages of producing genetically modified crops are:
• Danger of introducing undesirable variety as a result of a destructive combination
• There is a threat of producing super weeds
• There is a high risk of non-reproduction from genetically modified crops
• The chemicals that are produced, may cause a rejection in the human insecticides
• Genetically modified crops affect human health as they supply allergens and several other antibiotic resistance markers in the body
• These crops can affect the native biodiversity in an area as they can cause genetic pollution in the wild relatives of crop plants.
For instance, the Bt toxin is posing a threat, which is used to decrease the amount of pesticide for the benefit of insect pollinators such as the honey bee. If the gene expressed for Bt toxin gets expressed in the pollen, the honey bee might get affected leading to the pollination by honey bees getting affected.
4. What are Cry proteins? Name an organism that produce it. How has man exploited this protein to his benefit?
Solution:
Cry proteins are the toxins encoded by cry genes and produced by the bacteria – Bacillus thuringiensis which contains these proteins in its inactive form. It gets activated due to the alkaline pH environment of the gut of the insect when it ingests the inactive toxin protein. This leads to the lysis of epithelial cells and ultimately the insect dies. Hence, we say that man has exploited this protein to produce some transgenic crops with the property of insect-resistance such as Bt corn, Bt cotton etc.
5. What is gene therapy? Illustrate using the example of adenosine deaminase (ADA) deficiency.
Solution:
The process of correction of malfunctioned genes either by inserting the desirable gene or repairing or manipulating them is referred to as gene therapy. It is a collection of methods which enables the correction of a gene defect. In this therapy, the gene is inserted into the cells and tissues of a person to treat a disease.
Adenosine deaminase deficiency (ADA) is a rare genetic disorder caused due to deletion of the gene for adenosine deaminase. This enzyme is critical for the normal functioning of the immune system. This disorder can be treated by gene therapy wherein the gene is transfected into early embryonic cells of the bone marrow for permanent utilization.
6. Digrammatically represent the experimental steps in cloning and expressing an human gene (say the gene for growth hormone) into a bacterium like E. coli?
Solution:
A technique of producing multiple identical copies of a particular template DNA is known as DNA cloning which involves the usage of a vector that carries the particular foreign DNA fragment to the host cell.
The working of cloning and transfer of gene for growth hormone into E.coli can be depicted as given below:
7. Can you suggest a method to remove oil (hydrocarbon) from seeds based on your understanding of rDNA technology and chemistry of oil?
Solution:
Recombinant DNA technology or rDNA is a technique which is used for the manipulation of the genetic material of an entity in order to obtain desired results. For this, the genes that are necessary for oil formation in seeds must be recognized. With the help of restriction endonucleases, required genes should be removed. The DNA thus obtained must be treated with DNA ligases to seal the broken ends of the DNA. When cultivated aseptically on a nutrient medium, these cells will differentiate into a new plant possessing seeds with no oil.
8. Find out from internet what is golden rice.
Solution:
Golden rice, a variety of rice, Oryza sativa is a genetically modified crop which is developed as a fortified food to supply them to areas where there is scarcity of dietary Vitamin A, as golden rice is richly supplied with Vitamin A. Golden rice consists of a precursor of pro-Vitamin A, known as the beta-carotene, inserted into the rice through the process of genetic engineering.
Rice plants synthesize the beta-carotene pigment naturally in its leaves but it is not found in the seed’s endosperm as the pigment aids in photosynthesis and photosynthesis does not take place in the endosperm. As the beta-carotene is a precursor of pro-vitamin A, it is inserted into the rice variety to compensate for the dearth of dietary Vitamin A. Compared to vitamin supplements, this is a simpler and low-priced alternative. But they are still not available for human consumption, as this variety of rice has faced a considerable opposition from environmental activists.
9. Does our blood have proteases and nucleases?
Solution:
No, blood does not have proteases and nucleases. But some proteases does exist in its inactive form. If it would have been found in blood and cells, it would have been digested.
10. Consult internet and find out how to make orally active protein pharmaceutical. What is the major problem to be encountered?
Solution:
Successfully manufactured orally active protein product are vaccines used to prevent infectious diseases such as herpes, hepatitis B, influenza and so on. The genes for antigen are isolated from bacteria and cultivated along with cut leaf portions in an antibiotic medium of a potato plant. Then the callus is formed and the transgenic/recombinant potato is acquired containing the vaccines.
But, protein pharmaceuticals can be degraded by proteases of the digestive system in the alimentary canal. Hence, if taken orally, it is essential to safeguard therapeutic proteins from proteases of digestive system. Such active protein pharmaceuticals, when orally taken, are encapsulated proteins or peptides in formulations or liposomes which facilitates their transfer also. These peptides or proteins are used as vaccines to treat various diseases.
But, oral administration of these proteins or peptides poses some problems related to it. Once these proteins are ingested, the proteases found in the stomach juices denature the proteins hence their effect is nullified.
Making of orally active protein pharmaceutical:
• Proteins are inserted in a tablet whose coating is made of a material which is not digested by the stomach’s acidic medium but dissolves in the intestines causing the proteins to get absorbed by villi of the intestine
This is to protect the therapeutic proteins with a covering which will get dissolved after it passes through the stomach
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