BIOLOGY Case study (4 Marks)

→ As traditional breeding techniques failed to keep pace with demand and to provide sufficiently fast and efficient systems for crop improvement, another technology called tissue culture got developed.
→ It was learnt by scientists, during 1950s, that whole plants could be regenerated from explants, i.e., any part of a plant taken out and grown in a test tube, under sterile conditions in special nutrient media.
→ This capacity to generate a whole plant from any cell/explant is called totipotency.
→ It is important to stress here that the nutrient medium must provide a carbon source such as sucrose and also inorganic salts, vitamins, amino acids and growth regulators like auxins, cytokinins etc.
→ By application of these methods it is possible to achieve propagation of a large number of plants in very short durations.
→ This called micro-propagation.
→ Each of these plants will be genetically identical to the original plant from which they were grown, i.e., they are somaclones.
→ Many important food plants like tomato, banana, apple, etc., have been produced on commercial scale using this method. Try to visit a tissue culture laboratory with your teacher to better understand and appreciate the process.
→ Another important application of the method is the recovery of healthy pltnts from diseased plants.
→ Even if the plant is infected with a virus, the meristem (apical and axillary) is free of virus.
→ Hence, one can remove the meristem and grow it in vitro to obtain virus-free plants. Scientists have succeeded in culturing meristems of banana. Sugarcane, potato. etc.
Somatic hybridisation :
→ Scientists have even isolated single cells from plants and after digesting their cell walls have been able to isolate naked protoplasts (surrounded by plasm membranes).
→ Isolated protoplasts from two different varieties of plants each having a desirable character - can be fused to get hybrid protoplasts, which can be further grown to form a new plant. These hybrides are called somatic hybrids while the process is called somatic hybridisation.
→ When a protoplast of tomato is fused with that potato, and then they are grown to form new hybrid plants combining tomato and potato characteristics.
→ Well this has been achieved - resulting in formation of pomato; unfortunately this plant did not have all the desired combination of characteristics for its commercial utilisation.

→ Gene therapy is a collection of methods that allows correction of a gene defect that has been diagnosed in a child/embryo.
→ Here by using DNA medicinal protein is produce which correct or treat the mutated Gene.
→ Here genes are inserted into a person's cells and tissues to treat a disease.
→ Correction of a genetic defect involves delivery of a normal gene in to the individual or embryo. to take over the function of and compensate for the non-functional gene.
→ Example- Adenosine deaminase deficiency
→ The first clinical gene therapy was given in 1990 to a 4-year old girl with adenosine deaminase (ADA) deficiency.
→ This enzyme is crucial for the immune system to function.
→ The disorder is caused due to the deletion of the gene for adenosine deaminase.
→ In some children ADA deficiency can be cured by bone marrow transplantation.
→ In others it can be treated by enzyme replacement therapy, in which functional ADA is given to the patient by injection.
→ But the problem with both of these approaches that they are not completely curative. As a first step towards gene therapy, 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, which are subsequently returned to the patient.
→ However, as these cells are not immortal, the patient requires periodic infusion of such genetically engineered lymphocytes.
→ However, if the gene isolate from marrow cells producing ADA is introduced into cells at early embryonic stages, it could be a permanent cure.

→ Certain companies are being granted 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/country.
Examples :
→ Rice is an important food grain, the presence of which goes back thousands of years in Asia's agricultural history.
→ There are an estimated 200,000 varieties of rice in India alone.
→ The diversity of rice in India is one of the richest in the world.
→ Basmati rice is distinct for its unique aroma and flavour and 27 documented varieties of Basmati are grown in India.
→ There is reference to Basmati in ancient texts, folklore and poetry, as it has been grown for centuries..
→ 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, in the US and abroad.
→ This 'new' variety of Basmati had actually been derived from Indian farmer's varieties.
→ Indian Basmati was crossed with semi-dwarf varieties and claimed as an invention or a novelty.
→ The patent extends to functional equivalents, implying that other people selling Basmati rice could be restricted by the patent.
→ Several attempts have also been made to patent uses.
→ products and processes based on Indian traditional herbal medicines, e.g., turmeric, neem other countries/individuals may encash on our rich legacy and we may not be able to do anything about it.

→ For effective treatment of a disease, early diagnosis and understanding its pathophysiology is very important.
→ Using conventional methods of diagnosis (serum and urine analysis, etc.) early detection is not possible.
→ Recombinant DNA technology, Polymerase Chain Reaction (PCR) and Enzyme Linked Immunosorbent Assay (ELISA) are some of the techniques that serve the purpose of early diagnosis.
→ Presence of a pathogen (bacteria, viruses, etc.) is normally suspected only when the pathogen has produced a disease symptom. By this time the concentration of pathogen is already very high in the body.
Diagnosis by PCR :
→ However, very low concentration of a bacteria or virus at a time when the symptoms of the disease are not yet visible can be detected by amplification of their nucleic acid by PCR.
→ PCR is now routinely used to detect HIV in suspected AIDS patients.
→ It is being used to detect mutations in genes in suspected cancer patients too.
→ It is a powerful technique to identify many other genetic disorders.
Diagnosis by probes :
→ A single stranded DNA or RNA, tagged with a radioactive molecule (probe) is allowed to hybridise to its complementary DNA in a clone of cells followed by detection using autoradiography.
→ The clone having the mutated gene will hence not appear on the photographic film, because the probe will not have complementarity with the mutated gene.
Diagnosis by ELISA :
→ ELISA is based on the principle of antigen- antibody interaction.
→ Infection by pathogen can be detected by the presence of antigens (proteins, glycoproteins, etc.) or by detecting the antibodies synthesized against the pathogen.

→ Insulin is produced by beta cells of pancreas.
→ Insulin plays important role in a sugar or carbohydrate metabolism.
→ Due to lack of insulin diabetes mellitus occurs in humans.
→ Insulin used for diabetes was earlier extracted from pancreas of slaughtered cattle and pigs.
→ Insulin from an animal source, though caused some patients to develop allergy or other types of reactions to the foreign protein.

→ Insulin consists of two short polypeptide chains: chain A and chain B.
→ Polypeptide Chain A contains 21 amino acids and chain B contains 30 amino acids that are linked together by disulphide bridges.
→ In mammals, including humans, insulin is synthesised as a pro-hormone (like a pro-enzyme, the pro-hormone also needs to be processed before it becomes a fully mature and functional hormone) which contains an extra stretch called the C peptide.
→ This C peptide is not present in the mature insulin and is removed during maturation into insulin.
→ The main challenge for production of insulin using rDNA techniques was getting insulin assembled into a mature form.
→ In 1983, Eli Lilly an American company prepared two DNA sequences corresponding to A and B, chains of human insulin and introduced them in plasmids of E. coli to produce insulin chains.
→ Chains A and B were produced separately, extracted and combined by creating disulfide bonds to form human insulin.