Biotechnology & Its Applications

Biotechnology applications span human health, agriculture, transgenic organisms, and ethical governance. NEET frequently tests Bt crop gene names, gene therapy principles, and diagnostic techniques.

Genetically engineered insulin was a milestone. Human insulin consists of proinsulin cleaved into an A chain (21 amino acids) and a B chain (30 amino acids) after removal of the C peptide. In 1983, Eli Lilly commercially produced recombinant insulin by inserting separate A and B chain genes into E. coli plasmids, expressing each chain independently, and then assembling them through disulfide bonds. This replaced animal-source insulin from pigs and cattle, which caused allergic reactions due to slight structural differences.

Gene therapy corrects genetic defects by delivering a functional gene into a patient's cells. The first approved case was ADA (adenosine deaminase) deficiency, a severe combined immunodeficiency. Lymphocytes from the patient are harvested, a functional ADA gene is delivered via a retroviral vector, and the corrected lymphocytes are reinfused. However, since lymphocytes are not immortal, repeated infusions are necessary unless a bone marrow transplant (the permanent cure) is performed. PEG-ADA enzyme injection serves as an interim alternative.

Molecular diagnostics enable early and sensitive disease detection. PCR amplifies even trace amounts of pathogen DNA for detection, crucial for early-stage HIV diagnosis and genetic disorder screening. ELISA (Enzyme-Linked Immunosorbent Assay) detects antigens or antibodies through an enzyme-linked color change reaction, used for HIV, hepatitis B, and pregnancy testing. Autoradiography uses radioactive probes to detect specific DNA or RNA sequences on a membrane.

Bt crops express insecticidal Cry protein genes from Bacillus thuringiensis. The critical gene-crop associations are: Bt cotton carries cry1Ac and cry2Ab (targeting cotton bollworm, a lepidopteran pest), while Bt corn carries cry1Ab (targeting European corn borer, also lepidopteran). Inside the bacterium, the Cry protein exists as an inactive crystalline protoxin. When ingested by an insect larva, the alkaline pH of its gut activates the protoxin into active Bt toxin, which binds to midgut epithelial cell receptors, creates pores, causes cell swelling and lysis, and kills the insect.

RNA interference (RNAi) is a gene-silencing mechanism using double-stranded RNA (dsRNA). In tobacco plants engineered against the nematode Meloidogyne incognita, complementary sense and antisense RNA sequences are produced in the host, forming dsRNA that silences essential nematode genes, preventing infection.

Golden Rice was engineered to produce $\beta$-carotene (provitamin A) in the rice endosperm to combat vitamin A deficiency. The Flavr Savr tomato was the first commercially grown GM food, engineered for delayed ripening.

Transgenic animals serve multiple purposes: producing human therapeutic proteins (Rosie, the first transgenic cow, produced human $\alpha$-lactalbumin-enriched milk; transgenic sheep produce $\alpha$-1-antitrypsin for emphysema treatment), modeling human diseases (cancer, Alzheimer's in transgenic mice), and testing vaccine safety.

Biosafety concerns include unintended gene flow to wild relatives, allergenicity of GM foods, and environmental risks. India's GEAC (Genetic Engineering Approval Committee) regulates GMO field trials and commercial release. Biopiracy — unauthorized exploitation of biological resources — is illustrated by patent controversies over neem (patented by a European company), turmeric (wound-healing patent by University of Mississippi, later revoked), and basmati rice (RiceTec's patent on certain strains).

The key testable concept is the Bt toxin activation mechanism (inactive protoxin in bacterium, activated in insect's alkaline gut) and the precise cry gene-crop matching (cry1Ac/cry2Ab for cotton, cry1Ab for corn).