Biotechnological Applications in Medicine

Biotechnological applications in medicine use recombinant DNA technology to make safe drugs and to detect disease early. Following the NCERT Class 12 chapter, this page covers genetically engineered human insulin (proinsulin, C peptide and the 1983 Eli Lilly method), gene therapy for ADA deficiency, molecular diagnosis by PCR, probes and ELISA, transgenic animals, and ethical issues such as GEAC, the Basmati patent and biopiracy. NEET often asks the insulin chains, the first gene therapy and the uses of transgenic animals in questions on biotechnological applications in medicine.

1. Recombinant Therapeutics

• Recombinant DNA processes have had an immense impact on healthcare.
• They allow mass production of safe and more effective therapeutic drugs.
• ★ Exam imp Recombinant therapeutics do not induce unwanted immunological responses, which are common with similar products from non-human sources.
• They are identical to human proteins and are free from the risk of infection seen with products from non-human sources.
• About 30 recombinant therapeutics are approved for human use worldwide.
• In India, 12 of these are presently marketed.

2. Genetically Engineered Insulin

2.1 The need

• Adult-onset diabetes can be managed by taking insulin at regular time intervals.
• ★ Exam imp Insulin for diabetes was earlier extracted from the pancreas of slaughtered cattle and pigs.
• Animal insulin caused some patients to develop allergy or other reactions to the foreign protein.
• A bacterium that makes human insulin could be grown in large quantity to give as much insulin as needed.

2.2 Structure of insulin

2.3 Proinsulin and the C peptide

• In mammals, including humans, insulin is synthesised as a pro-hormone (proinsulin).
• Like a pro-enzyme, the pro-hormone must be processed before it becomes a mature, functional hormone.
• ★ Exam imp Proinsulin contains an extra stretch called the C peptide.
• ★ Exam imp The C peptide is not present in mature insulin; it is removed during maturation.

2.4 Making human insulin by rDNA technology

• The main challenge was getting insulin assembled into a mature form.

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

• ★ Exam imp Human insulin is made in bacteria, yet its structure is absolutely identical to that of the natural molecule.

3. Gene Therapy

• It is an attempt to correct a hereditary disease that a person is born with.
• A normal gene is delivered into the individual or embryo.
• The normal gene takes over the function of the non-functional gene and compensates for it.
• It may replace a defective mutant allele with a functional one, or use gene targeting, which involves gene amplification.
• Viruses that attack their hosts and introduce their genetic material into host cells are used as vectors to transfer healthy genes, or portions of genes.

3.1 ADA deficiency: the first gene therapy

• ★ Exam imp The first clinical gene therapy was given in 1990 to a 4-year-old girl with adenosine deaminase (ADA) deficiency.
• The ADA enzyme is crucial for the immune system to function.
• The disorder is caused by deletion of the gene for adenosine deaminase.

3.2 Steps of gene therapy for ADA deficiency

1. Lymphocytes from the patient's blood are grown in a culture outside the body.
2. A functional ADA cDNA is introduced into these lymphocytes using a retroviral vector.
3. The lymphocytes are returned to the patient.
4. These cells are not immortal, so the patient needs periodic infusion of such genetically engineered lymphocytes.

4. Molecular Diagnosis

• Effective treatment needs early diagnosis and an understanding of the disease's pathophysiology.
• Conventional methods, such as serum and urine analysis, cannot detect disease early.
• ★ Exam imp Techniques for early diagnosis: recombinant DNA technology, Polymerase Chain Reaction (PCR) and Enzyme Linked Immuno-sorbent Assay (ELISA).

4.1 PCR

• A pathogen (bacteria, viruses and so on) is normally suspected only after it has produced a disease symptom.
• By then, the concentration of the pathogen in the body is already very high.
• A very low concentration of a bacterium or virus, before symptoms appear, can be detected by amplifying its nucleic acid by PCR.
• PCR makes many copies of the nucleic acid, so even a tiny amount becomes enough to detect.

4.2 Probe and autoradiography

1. A single-stranded DNA or RNA is tagged with a radioactive molecule; this is the probe.
2. The probe is allowed to hybridise to its complementary DNA in a clone of cells.
3. Hybridisation is detected by autoradiography.
4. A clone with the mutated gene does not appear on the photographic film, because the probe is not complementary to the mutated gene.

4.3 ELISA

• ★ Exam imp ELISA is based on the principle of antigen-antibody interaction.
• Infection is detected by the presence of antigens (proteins, glycoproteins and so on) of the pathogen.
• Or, infection is detected by the antibodies synthesised against the pathogen.

5. Transgenic Animals

• Transgenic rats, rabbits, pigs, sheep, cows and fish have been produced.
• ★ Exam imp Over 95 per cent of all existing transgenic animals are mice.

5.1 Why transgenic animals are produced

5.2 Rosie, the first transgenic cow

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

6. Ethical Issues

6.1 The need for regulation

• Human manipulation of living organisms cannot go on further without regulation.
• Ethical standards are needed to judge the morality of human activities that might help or harm living organisms.
• Biological significance also matters: GM organisms may have unpredictable results when introduced into the ecosystem.
• The current interest in manipulating microbes, plants and animals has raised serious ethical questions.

• ★ Exam imp The Indian Government has set up organisations such as GEAC (Genetic Engineering Approval Committee).
• GEAC decides the validity of GM research and the safety of introducing GM organisms for public services.

6.2 Patents on biological resources

• Using living organisms for public services, such as food and medicine sources, has created problems with patents.
• There is growing public anger at patents given to companies for products and technologies that use genetic materials, plants and other biological resources.
• These resources had long been identified, developed and used by farmers and indigenous people of a region or country.

6.3 The Basmati case

• Rice is an important food grain, grown for thousands of years in Asia.
• India has an estimated 200,000 varieties of rice; its rice diversity is one of the richest in the world.
• Basmati rice is distinct for its unique aroma and flavour.
• ★ Exam imp 27 documented varieties of Basmati are grown in India.
• Basmati is referred to in ancient texts, folklore and poetry, as it has been grown for centuries.
• ★ Exam imp In 1997, an American company got patent rights on Basmati rice through the US Patent and Trademark Office.
• This let the company sell a 'new' variety of Basmati in the US and abroad.
• The 'new' variety was derived from Indian farmers' varieties: Indian Basmati was crossed with semi-dwarf varieties and claimed as an invention.
• The patent extends to functional equivalents, so others selling Basmati could be restricted.
• Attempts have also been made to patent uses, products and processes based on Indian herbal medicines, such as turmeric and neem.
• Unless such applications are countered quickly, other countries or individuals may encash our rich legacy.

6.4 Biopiracy

• Traditional knowledge of bio-resources can be used to develop modern applications.
• It can also save time, effort and expenditure during commercialisation.
• There is a growing realisation of injustice, inadequate compensation and benefit sharing between developed and developing countries.
• So some nations are developing laws to prevent unauthorised exploitation of their bio-resources and traditional knowledge.
• The Indian Parliament cleared the second amendment of the Indian Patents Bill.
• The amendment takes such issues into consideration, including patent terms, emergency provisions, and research and development initiatives.

7. Exam Essentials

Pairs to Match

Numbers to Remember

• Recombinant therapeutics: about 30 approved worldwide; 12 marketed in India.
• Insulin: 2 polypeptide chains (A and B).
• rDNA human insulin by Eli Lilly: 1983.
• First clinical gene therapy: 1990, a 4-year-old girl with ADA deficiency.
• Transgenic animals that are mice: over 95 per cent.
• Rosie, the first transgenic cow: 1997; 2.4 g of human protein per litre of milk.
• Rice varieties in India: about 200,000; documented Basmati varieties: 27.
• US patent on Basmati: 1997.

Examples to Remember

8. Quick Revision

• Recombinant therapeutics: safe, effective, identical to human proteins, no unwanted immune response.
• About 30 recombinant therapeutics approved worldwide; 12 marketed in India.
• Animal insulin from cattle and pig pancreas caused allergy in some patients.
• Insulin: chains A and B joined by disulphide bridges.
• Proinsulin carries a C peptide that is removed during maturation.
• Eli Lilly, 1983: separate A and B chains made in E. coli, then joined.
• Gene therapy delivers a normal gene to correct a defect diagnosed in a child or embryo.
• First gene therapy: 1990, 4-year-old girl with ADA deficiency (gene deleted).
• ADA cDNA enters cultured lymphocytes by a retroviral vector; infusion is repeated.
• Possible permanent cure: ADA gene from marrow cells into early embryonic cells.
• PCR amplifies nucleic acid; detects HIV and cancer mutations early.
• Radioactive probe and autoradiography: the mutated clone gives no signal.
• ELISA: antigen-antibody interaction; detects antigens or antibodies.
• Transgenic animals express a foreign gene; over 95 per cent are mice.
• GEAC regulates GM work; Basmati patent (1997) and turmeric, neem show biopiracy.

9. Solved Examples

10. Practice Questions

Common Mistakes to Avoid