Genomics and personalised medicine

The first principle

Any two people share about 99.9 per cent of their DNA, and almost everything that makes medicine work differently in different people lies in the remaining fraction. Reading a person's genome lets a doctor see some of those differences directly, which is why medicine can move from treating the average patient to treating the actual one. The catch is that a variant means something only when it is compared with many others from the same population, so personalised medicine for Indians depends on a large, well governed collection of Indian genomes.

The core

What a genome is and how it is read

• The genome is the full set of DNA in a cell. The human nuclear genome has about 3.1 billion base pairs on 23 pairs of chromosomes and about 20,000 genes that code for proteins, which make up less than 2 per cent of it; the rest includes switches that control genes. A small separate genome, inherited only from the mother, sits in the mitochondria. How DNA stores and copies information is set out in the DNA and genetic engineering note.
• Sequencing means reading the order of bases. Next generation sequencing breaks DNA into millions of short fragments, reads them all in parallel and uses software to align them against a reference genome, so a whole human genome can now be read in about a day.
• The cost collapse made genomics routine. The Human Genome Project, completed in 2003, took 13 years and about 2.7 billion US dollars, while a genome can now be sequenced for a few hundred dollars, which is why sequencing has moved from research into hospitals and disease surveillance.
• What the reading finds is variation. A single nucleotide variant changes one letter, an insertion or deletion adds or removes a few, and a structural variant moves or copies a large block; most variants are harmless, some change how a drug works, and a few cause disease on their own.

From genome to treatment

• Personalised or precision medicine uses a person's genes, together with their environment and lifestyle, to choose prevention and treatment, instead of giving everyone the same dose of the same drug.
• Pharmacogenomics studies how genes change the response to drugs. Variants in liver enzymes decide how fast warfarin or clopidogrel is processed, and the HLA-B\*15:02 variant, found in several Asian populations including some Indian groups, raises the risk of a severe skin reaction to the epilepsy drug carbamazepine, so a test before prescribing can prevent harm.
• Cancer genomics reads the tumour's mutations to choose a targeted drug, and a liquid biopsy finds fragments of tumour DNA in blood, so a cancer can be detected or tracked without cutting tissue.
• Genetic diagnosis and screening find the cause of rare inherited disease, test newborns and carriers, and allow prenatal diagnosis of conditions such as thalassaemia and sickle cell disease.
• Polygenic risk scores add up the small effects of many variants to estimate the risk of common diseases such as diabetes or heart disease, but scores built mostly on European data predict poorly for Indians.

Dimensions

• Health. Most rare diseases are genetic, and India's high rate of marriage within communities makes some recessive disorders far more common in particular groups, so knowing the variants of each group allows targeted screening and counselling.
• Scientific. Indians are under represented in global genomic databases, so variants common in India may be wrongly labelled as rare or harmful; an Indian reference fixes this for the world as well.
• Economic. Genomic diagnostics, cancer tests and drug discovery are a fast growing industry, and an Indian dataset is an asset for Indian firms, as the bioeconomy note explains.
• Ethical and legal. A genome reveals information about a person's relatives, ancestry and future disease, it cannot be changed if leaked, and it can be misused by insurers or employers, so consent, privacy and protection from discrimination matter more than for most data.
• Public health. Sequencing pathogens shows how a virus mutates and spreads and how resistant bacteria travel, as the antimicrobial resistance note discusses.

In practice

• IndiGen (2019 to 2020). The Council of Scientific and Industrial Research (CSIR), through its Institute of Genomics and Integrative Biology, sequenced 1,029 healthy Indians as a pilot and found more than 18 million variants not seen in the main global databases, which showed how much Indian variation was missing.
• GenomeIndia (from 2020). Funded by the Department of Biotechnology (DBT) and run by a consortium of research institutions, it sequenced the whole genomes of about 10,000 healthy, unrelated Indians from 83 population groups, tribal and non tribal, and released the data in January 2025; the consortium reported about 180 million variants before quality filtering. Its long term aim is to scale up to a million genomes.
• The Indian Biological Data Centre (IBDC), dedicated in November 2022 at the Regional Centre for Biotechnology in Faridabad with a disaster recovery site at the National Informatics Centre in Bhubaneswar, is the national store for life science data. Under DBT's Biotech-PRIDE (Promotion of Research and Innovation through Data Exchange) Guidelines of 2021, data from publicly funded research must be deposited there, and researchers obtain the GenomeIndia data through a controlled access process rather than an open download.
• Genomic surveillance. The Indian SARS-CoV-2 Genomics Consortium (INSACOG), set up in December 2020, linked national laboratories to sequence samples of the Covid virus and track variants, and it is the template for watching other pathogens.
• The National Sickle Cell Anaemia Elimination Mission, launched on 1 July 2023 at Shahdol in Madhya Pradesh, aims to end sickle cell disease as a public health problem by 2047 through screening, counselling and care in 17 high focus States, mostly in tribal areas; a genetic test is the core of the programme.
• Three parent babies. Mitochondrial replacement therapy moves the nucleus from a mother's egg or embryo, whose mitochondria carry a disease, into a donor egg or embryo with healthy mitochondria, so the child has nuclear DNA from both parents and mitochondrial DNA, about 37 genes, from the donor. The United Kingdom legalised it in 2015, and researchers in Newcastle reported eight babies born by this method in 2025. India's stem cell guidelines prohibit implanting an embryo manipulated in the laboratory, so the technique is not available here.

Issues and way forward

• Privacy and consent. Genetic data identifies a person and their family for life, and the Digital Personal Data Protection Act 2023 treats it only as ordinary personal data, without a separate category for genetic data; a specific law or rules on genetic data, with strict limits on use by insurers and employers, is the gap.
• Discrimination. Results that show a high risk of disease could be used to deny jobs or insurance, so a legal bar on genetic discrimination, of the kind the United States adopted in 2008, should accompany wider testing.
• Interpreting variants. Most variants found in a patient are of uncertain meaning, and India has few clinical geneticists and genetic counsellors, so training counsellors and building Indian variant databases must keep pace with sequencing.
• Access and cost. Genomic tests are sold mainly in private hospitals in large cities, while the burden of inherited disease is heaviest in rural and tribal India; public screening programmes, like the sickle cell mission, and lower test prices through Indian manufacture can spread the benefit.
• Benefit sharing. Communities whose DNA builds a database have a claim on what is made from it, so terms for commercial use and for returning benefits, such as free screening, should be written in advance.

Common confusions

• Genetics and genomics. Genetics studies single genes and how they are inherited, while genomics studies the whole genome and how genes work together.
• Genome and exome. The genome is all of the DNA, while the exome is the 1 to 2 per cent of it that codes for proteins, where most known disease causing variants lie.
• Personalised and precision medicine. The terms are used almost interchangeably, but precision medicine is the preferred term because treatment is matched to groups of patients who share a feature, not designed separately for each person.
• Three parent babies and gene editing. Mitochondrial replacement swaps whole mitochondria and changes no gene, while gene editing changes a chosen DNA sequence.
• GenomeIndia and the Human Genome Project. The Human Genome Project produced one reference sequence of the human genome, while GenomeIndia maps variation across Indian populations against that reference.

For the exam

• Keyword bank: whole genome sequencing, next generation sequencing, reference genome, genetic variant, GenomeIndia, Indian Biological Data Centre, Biotech-PRIDE, pharmacogenomics, precision medicine, liquid biopsy, genomic surveillance, biobank, mitochondrial replacement therapy, genetic privacy, benefit sharing.
• Previous year questions: Practise the previous year questions on this topic →
• Use in an answer:
  • Introduction with data: GenomeIndia sequenced about 10,000 healthy Indians from 83 population groups and released the data in January 2025, giving India a reference for its own genetic variation.
  • Introduction with a source: The IndiGen study of CSIR found that about a third of the variants in 1,029 Indian genomes were absent from the major global databases, showing why medicine built on others' data can fail Indian patients.
  • Conclusion: Genomics can make Indian medicine more precise and cheaper, provided the data that make it possible are protected by a genetic privacy law and shared fairly with the communities that gave them.
  • Conclusion: The next step after mapping Indian genomes is to put them to work in public screening, drug safety testing and disease surveillance, so that the benefit reaches the tribal village as well as the city hospital.