Biotechnology in Medicine

NCERT grounding

NCERT Class XII Biology, Chapter 10, opens Section 10.2 with the operative claim that recombinant DNA technological processes have made immense impact in the area of healthcare by enabling mass production of safe and more effective therapeutic drugs. Three named applications follow — genetically engineered insulin (10.2.1), gene therapy (10.2.2) and molecular diagnosis (10.2.3). The NIOS supplement (Lesson 30) widens the same idea to vaccines, antibiotics, vitamins and interferons. Together they fix the four numbers and four arms that NEET asks repeatedly.

"At present, about 30 recombinant therapeutics have been approved for human-use the world over. In India, 12 of these are presently being marketed."

NCERT Class XII · Section 10.2

The biotech-medicine landscape

Before the recombinant era, therapeutic proteins were extracted from animal tissue or human cadavers — insulin from cattle and pig pancreas, growth hormone from human pituitaries, clotting factor VIII pooled from donor plasma. Each route was scarce, expensive and immunologically unsafe. Animal-source insulin triggered allergic reactions in many patients; cadaver-derived growth hormone transmitted Creutzfeldt–Jakob disease; pooled plasma factor VIII spread hepatitis and HIV in the 1980s. The recombinant route solved all three problems simultaneously by letting microbes or yeast express human genes inside fermenters.

The pay-off is that the protein produced is structurally identical to the native human molecule, so it does not elicit unwanted immunological responses. It is also free from the risk of cross-species infection because the host organism (E. coli, yeast, CHO cells) is grown under controlled conditions with no human or animal pathogen contact. This is why NCERT calls the impact "immense" and why the chapter summary highlights insulin as the canonical case study.

The discipline is conventionally split into four arms for NEET: recombinant therapeutic proteins, recombinant vaccines, gene therapy, and molecular diagnosis. Around the edges sit three extension applications — monoclonal antibody therapy, interferon therapy, and stem-cell therapy. The same NCERT numbers (≈30 worldwide, 12 in India) cover all the protein and vaccine products.

Recombinant therapeutic proteins

The protein arm of biotech medicine treats deficiency disorders by manufacturing the missing human protein in a microbial or mammalian-cell host. The host's ribosomes read a cloned human gene and secrete the protein into culture medium, from where it is purified by downstream processing. Four product families dominate NEET-grade discussion.

Human insulin

Insulin is the textbook case. In 1983, Eli Lilly chemically synthesised the two DNA sequences corresponding to chain A and chain B of human insulin, inserted them into plasmids of E. coli, expressed the chains separately, and combined them by creating disulphide bridges. This bypassed the natural pro-insulin pathway entirely — the recombinant product has no C-peptide because the C-peptide is never made. Modern biosimilars often use the yeast Saccharomyces cerevisiae instead, which can fold and secrete the insulin precursor in one fermentation.

Human growth hormone

Before recombinant production, growth hormone was extracted from cadaver pituitary glands and given to children with hypopituitary dwarfism. The supply was tiny — a few hundred pituitaries per patient per year — and several recipients developed Creutzfeldt–Jakob disease from prion-contaminated material. Recombinant human growth hormone, somatotropin, is now expressed in E. coli and is the standard of care; the recombinant route eliminates both scarcity and prion risk.

Clotting factors VIII and IX

Haemophilia A and B arise from deficiency of clotting factors VIII and IX respectively. Patients historically received the missing factor as a pooled plasma concentrate, which in the 1980s transmitted hepatitis C and HIV across an entire generation of haemophiliacs. Recombinant factor VIII and factor IX, produced in mammalian cell culture (typically Chinese hamster ovary cells), are now used worldwide because they are virally clean by manufacture.

Other proteins

The same logic extends to erythropoietin (for chronic-kidney-disease anaemia), follicle-stimulating hormone (for assisted reproduction), tissue plasminogen activator (for clot lysis after myocardial infarction), and α-1-antitrypsin (for emphysema, produced famously in transgenic sheep and cow milk). NEET has asked α-1-antitrypsin and emphysema in 2024.

Recombinant vaccines

A recombinant subunit vaccine presents only one or two antigens of a pathogen — never the live or whole-killed organism — so it cannot cause the disease it protects against. The clearest example is the hepatitis-B vaccine. The gene encoding the hepatitis-B surface antigen (HBsAg) is cloned into the yeast Saccharomyces cerevisiae. The yeast secretes HBsAg, which is purified and formulated as the vaccine. This was the first recombinant vaccine licensed for human use (1986) and remains the textbook example.

Compared with plasma-derived vaccines of the 1970s — which were prepared from HBsAg-positive human serum and carried a residual risk of contamination by HIV and other blood-borne pathogens — the yeast-derived product is completely free of human source material. The same recombinant strategy is used today for the HPV vaccine (L1 protein in yeast) and several COVID-19 subunit vaccines.

Gene therapy

Gene therapy is the third arm and the only one that fixes the genetic defect itself rather than supplying the missing protein. NCERT defines it as "a collection of methods that allows correction of a gene defect that has been diagnosed in a child/embryo," achieved by inserting a normal gene into the patient's cells to compensate for the non-functional gene.

Two NEET-favourite facts attach to this case. First, ADA deficiency is caused by deletion of the gene for adenosine deaminase, an enzyme crucial for immune-system function — its absence causes severe combined immunodeficiency. Second, mature lymphocytes are not immortal, so the engineered cells die over weeks and the patient must be re-infused periodically. NCERT signals that introducing the ADA gene at the early embryonic stage could in principle give a permanent cure.

Molecular diagnosis

The fourth arm shifts from cure to detection. Conventional methods — serum analysis, urine analysis, microbial culture — register a pathogen only when it has already multiplied to symptomatic levels. Recombinant DNA technology, Polymerase Chain Reaction (PCR) and Enzyme-Linked Immuno-Sorbent Assay (ELISA) push detection forward to the pre-symptomatic phase by amplifying signal rather than waiting for it to rise.

PCR is the workhorse of molecular diagnostics. By amplifying even a few copies of pathogen DNA or RNA to billions, it can detect HIV in suspected AIDS patients well before seroconversion, register SARS-CoV-2 RNA before symptoms appear, and identify oncogenic mutations in suspected cancer patients. ELISA, by contrast, exploits the antigen–antibody interaction: an antibody bound to an enzyme produces a colour change when it binds its target, allowing detection of either the pathogen's antigen or the host's antibody response.

The radioactive-probe technique is the third tool. A single-stranded DNA or RNA tagged with a radioactive isotope is allowed to hybridise to its complementary sequence in a clone of cells, then visualised by autoradiography. If the gene of interest is mutated, the probe fails to bind and the clone does not appear on the photographic film — a negative result identifies the mutation. NEET 2021 (Q.150) tests this exact mechanism.

Monoclonals, interferons & stem cells

Around the four NCERT arms sit three extension applications that NEET treats as recognition-level material. They are not in the Class XII chapter text, but they are routinely listed in the NIOS supplement and in chapter-end summaries of biotech medicine, so a NEET aspirant must know what each does and how it is produced.

Monoclonal antibodies

A monoclonal antibody is one that recognises a single specific epitope on its target. It is produced by hybridoma technology — fusing an antibody-producing B-cell with a myeloma cell to create an immortal clone that secretes one antibody for ever. In medicine, monoclonals are used both diagnostically (as the recognition element in ELISA, lateral-flow tests, immunohistochemistry) and therapeutically (rituximab and trastuzumab in cancer; infliximab in autoimmune disease). The same molecule type that runs your ELISA is also the molecule that targets a tumour antigen.

Interferons

Interferons are naturally secreted cytokines that activate antiviral defences and immune surveillance. Recombinant interferon-α is used to treat chronic hepatitis B and hepatitis C; recombinant interferon-β is used in multiple sclerosis; interferon-γ is used in chronic granulomatous disease. Cancer applications include hairy-cell leukaemia and certain melanomas. The proteins are produced in microbial hosts using the same rDNA pipeline as insulin.

Stem-cell therapy

Stem cells — bone-marrow-derived haematopoietic stem cells, umbilical-cord-blood stem cells, and induced pluripotent stem cells — are used to reconstitute the haematopoietic system after chemotherapy (bone-marrow transplant for leukaemia) and are under active development for regenerative therapy of spinal-cord injury, retinal degeneration and type-1 diabetes. NCERT mentions bone-marrow transplant only as an alternative to ADA gene therapy, but stem cells appear in broader NEET reading.

Worked examples

Common confusion & NEET traps