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BharatGenome

Supporting section

Learn genomics by travelling through it

A 18-chapter journey, controlled entirely by scrolling. It starts inside a single molecule and ends at the question BharatGenome exists to answer. No biology background is assumed.

NucleotideDNAGeneChromosomeGenomeGenetic variationAllele frequencyReference genomeBharatGenome

0118The molecule

Nucleotide

A nucleotide is one building block of DNA: a phosphate group, a sugar, and a nitrogenous base, joined together.

Why it matters — Chain millions of them end to end and you have a strand of DNA.

NucleotidePhosphateSugarBase

0218The molecule

A, T, G, C

DNA uses four bases — adenine, thymine, guanine and cytosine. Adenine always pairs with thymine, and guanine always pairs with cytosine.

A–T · G–C

Why it matters — Because the pairing is fixed, one strand always predicts the other.

AdenineThymineGuanineCytosineBase pair

0318The molecule

DNA

DNA is a long molecule of two complementary strands of nucleotides, wound around each other into a double helix.

Why it matters — Every idea in the rest of this page is about differences in this one molecule.

DNADouble helixStrand

0418Reading it

DNA sequence

The sequence is the order in which the bases occur along a strand.

A T G C A A T G — illustrative sequence

Why it matters — The information is carried by the order, not by the letters themselves.

Illustrative — not real dataDNA sequence

0518Reading it

Gene

A gene is a region of DNA that carries the information for a functional product, such as a protein or a functional RNA.

Why it matters — A gene is a stretch of the molecule, not a separate object floating beside it. Most of the genome lies outside genes.

Gene

0618Packaging

Chromosome

A chromosome is DNA wound around proteins and packaged into one organised structure.

Why it matters — Packaging is how roughly two metres of DNA fits inside a single cell nucleus.

ChromosomeDNA packagingChromatin

0718Packaging

Genome

A genome is the complete set of genetic material in an organism — every chromosome, every gene, and everything in between.

Why it matters — Nucleotide, DNA, gene, chromosome, genome: one thing nested inside the next.

GenomeKaryotype

0818Packaging

The human genome

A human genome is about three billion base pairs, held in 23 chromosome pairs, in almost every cell of the body.

Why it matters — Everybody carries one. No two are identical.

Human genomeBase pair

0918Difference

Genetic variation

Genetic variation is the difference in DNA sequence between individuals.

Why it matters — Any two people are more than 99% identical in sequence. Variation is the remainder.

Genetic variation

1018Difference

Variant

A variant is a position where one sequence differs from the sequence it is being compared against.

A T G C · A A T G A T G C · G A T G

Why it matters — A variant is not automatically harmful, protective, or meaningful. Most have no known effect at all.

Illustrative — not real dataVariantSNP

1118Difference

Allele

An allele is one of the alternative versions of a sequence found at a given position.

Why it matters — If some people carry A at a position and others carry G, then A and G are its two alleles.

Illustrative — not real dataAllele

1218Populations

Population

A population is a group of individuals considered together when studying genetic variation.

Why it matters — A population is defined by the study that measures it, not by how anyone looks. It is a useful grouping with real limits.

Population

1318Populations

Allele frequency

Allele frequency is how common one allele is within a population.

A 60% · G 40% — illustrative

Why it matters — It is always a statement about a specific group of people. Ask a different group and the number can change.

Illustrative — not real dataAllele frequency

1418Populations

Populations are not identical

The same position can carry very different allele frequencies in different populations.

same position · three populations · illustrative

Why it matters — A variant that is uncommon in one population may be common in another — which is why the population a number came from matters.

Illustrative — not real data

1518Representation

Reference genome

A reference genome is an agreed representative sequence, used as a shared standard for describing and comparing genomes.

Why it matters — It is a map everyone agrees on. It is not the genome of an average human, and not a 'correct' genome.

Reference genome

1618Representation

Genomic representation

Genomic representation is how well the diversity of real human populations is actually captured by the reference resources research depends on.

Why it matters — Reference resources have historically not represented all populations equally. Where that coverage is thin, population-specific variation can be missed, underrepresented, or harder to interpret.

Genomic representationReference panel

1718BharatGenome

India is extraordinarily diverse

India holds a large share of humanity and many long-separated populations, producing genetic structure that widely used reference resources cover thinly.

Why it matters — 'Indian' is itself a simplification — it is many populations, with deep structure between them.

1818BharatGenome

BharatGenome

BharatGenome exists so that genomic evidence for Indian populations can be read alongside global evidence, with the provenance and the limits of each number stated.

Why it matters — The problem is not that India needs a genome. It is that genomic interpretation should account for populations that reference resources have historically underrepresented.

What you just travelled through

One thing inside the next

Every level of that journey is contained in the one above it. This is the relationship worth keeping.

The hierarchy

  1. Genome
  2. Chromosomes
  3. DNA
  4. Genesa region of DNA
  5. DNA sequenceA T G C…
  6. Base pairs
  7. Nucleotides

A gene is a region of DNA. A chromosome is that DNA packaged. A genome is the complete set. Nothing on this list is a separate object from the one above it.

And why representation follows from it

  • People differ at specific positions. Those differences are variants, and each version found at a position is an allele.
  • Allele frequencies are per population. The same position can be common in one group and rare in another.
  • Reference resources are built from whoever was sequenced. Where a population is thinly covered, its variation is easier to miss and harder to interpret.
  • That is the gap BharatGenome reports on — not by claiming a number, but by putting Indian and global evidence side by side with their provenance attached.

That is the whole idea. The next step is to run it on a real gene or variant.

Reference

The vocabulary in full

The journey introduces the 18 ideas you need to read a comparison. These 23 entries are the rest of the vocabulary — the terms that appear in a result, in the literature, and in the methodology.

1 · The basics

The vocabulary for talking about what is inside a cell.

What is DNA?

DNA is a long chemical instruction manual carried inside almost every cell in your body. It holds the information a cell needs to build and run itself.

Think of it like…

a very long book written in a four-letter alphabet, copied into every room of a house.

Why this matters to BharatGenome

Everything BharatGenome compares is ultimately a difference in this text between groups of people.

A, C, G and T

DNA is written with only four letters — A, C, G and T, called bases. Their order along the strand is what carries the information.

Think of it like…

an alphabet with four letters instead of twenty-six. Meaning comes from the order, not the number of letters.

Why this matters to BharatGenome

When we say a population carries 'A' or 'G' at a position, these are the letters we mean.

What is a chromosome?

DNA is not one loose strand. It is packaged into 46 bundles called chromosomes — 23 inherited from each parent.

chr1chr2…chr22chrXchrY
Think of it like…

chapters of the book, each bound separately so the whole thing stays organised.

Why this matters to BharatGenome

A variant is located by chromosome and position — that coordinate is how two datasets know they are talking about the same spot.

What is a gene?

A gene is a stretch of DNA with a job — usually the recipe for one protein. Humans have roughly 20,000 of them.

MTHFRBRCA1CYP2C19HBB
Think of it like…

one recipe inside the cookbook. The whole book is not a recipe; a specific passage is.

Why this matters to BharatGenome

Searching a gene symbol in Explore is usually how a researcher starts, because genes are the unit most research is organised around.

What is a genome?

A genome is the complete set of DNA in one organism — all the chromosomes, all the genes, and everything in between.

Think of it like…

the entire cookbook, not just one recipe.

Why this matters to BharatGenome

'Genomic representation' is about whose whole genomes were read to build the datasets everyone else relies on.

2 · How people differ

Any two people are over 99% identical in DNA. This section is about the rest.

What is a genetic variant?

A variant is a spot where people's DNA differs — one letter swapped, or a short stretch inserted or deleted.

Think of it like…

a typo that appears in some printings of a book but not others. Most typos change nothing; a few change the meaning.

Why this matters to BharatGenome

Variants are the objects BharatGenome compares. How common a variant is can differ a lot between populations.

What is a SNP?

A SNP (single nucleotide polymorphism) is the most common kind of variant: exactly one letter differs, and that difference is reasonably common in at least some population.

Think of it like…

a single-character typo, as opposed to a whole missing paragraph.

Why this matters to BharatGenome

Most frequency comparisons — and most of the research that depends on them — are about SNPs.

What is an allele?

An allele is one of the alternative versions found at a variant position. If some people have A there and others have G, then A and G are the two alleles.

Think of it like…

the two spellings of a word that both appear in print — 'colour' and 'color'. Each spelling is an allele.

Why this matters to BharatGenome

The Indian-vs-global comparison is literally a comparison of how common each allele is.

What is a population?

In genomics, a population is a group of people studied together, usually because of shared ancestry or geography. A frequency is always a statement about a specific population.

Think of it like…

a survey sample. 'What do people think?' is meaningless until you say which people were asked.

Why this matters to BharatGenome

India is not one population — it is many, with deep structure. Even 'Indian' is a simplification, and BharatGenome says so on every result.

What is allele frequency?

Allele frequency is how common one allele is in a group of people, written as a percentage. If 60% of the copies counted in a group are A and 40% are G, those are the allele frequencies.

Think of it like…

asking a crowd which spelling they use and reporting the split. The answer describes that crowd — ask a different crowd and you may get a different split.

Why this matters to BharatGenome

This is the single number at the heart of BharatGenome. The whole product exists because it is not the same everywhere.

What is an rsID?

An rsID (like rs1801133) is a stable public identifier for a known variant, so different databases can refer to the same position without ambiguity.

Think of it like…

an ISBN for a book. Different shops, different catalogues, same number.

Why this matters to BharatGenome

It is the cleanest way to ask two different datasets about exactly the same variant — which is what a comparison requires.

Try it: pick a letter

This is a short stretch of DNA. Choose any base to see what a change at that position would mean.

Nothing changed yet — every person's copy reads the same here.

3 · Reference data

Where the numbers in genomics actually come from — and whom they describe.

What is a reference genome?

A reference genome is one agreed-upon sequence used as a shared coordinate system, so everyone can describe positions the same way. It is a map, not an ideal or 'correct' genome.

Think of it like…

street numbering for a city. Useful because everyone agrees on it, not because house number 1 is the best house.

Why this matters to BharatGenome

Coordinates come from the reference. It is a standard for locating things, and should not be read as what a genome 'should' look like.

What is a reference panel?

A reference panel is a collection of already-sequenced genomes used as a lookup table to fill in or interpret new data.

Think of it like…

a phrasebook compiled from certain speakers. It works well for dialects it covers and poorly for ones it does not.

Why this matters to BharatGenome

If a panel contains few Indian genomes, the results it produces for Indian samples are weaker — a direct, practical consequence of representation.

What is genotype imputation?

Imputation fills in variants that were not directly measured, by inferring them from nearby measured variants using a reference panel.

Think of it like…

autocomplete. It guesses the rest of the word from the letters typed — and it guesses much better in a language it was trained on.

Why this matters to BharatGenome

Imputation quality depends on the panel matching the person. Under-represented populations get less accurate imputation.

What is linkage disequilibrium?

Nearby variants tend to be inherited together, so knowing one often tells you about another. That statistical tendency is called linkage disequilibrium, or LD.

Think of it like…

words that usually travel together in a phrase. Hear the first and you can often guess the second — but which words pair up differs by dialect.

Why this matters to BharatGenome

LD patterns differ between populations, so a result anchored to one population's LD structure may not point at the same thing in another.

4 · What researchers build on top

The methods that inherit whatever population the underlying data came from.

What is GWAS?

A genome-wide association study scans many variants across many people to find positions statistically associated with a trait or condition.

Think of it like…

comparing two large groups' shopping lists to spot items that show up far more often in one.

Why this matters to BharatGenome

GWAS results reflect the cohort that was studied. If Indian cohorts are absent, the associations found may not be the ones that matter here.

What is a polygenic risk score?

A polygenic risk score adds up the small effects of many variants into a single number summarising a person's genetic predisposition relative to a studied group.

Think of it like…

a credit score built from many small signals — and calibrated on one particular set of customers.

Why this matters to BharatGenome

PRS are known to lose accuracy when applied to populations unlike the one they were derived from. That loss is the representation problem in its most visible form.

What is pharmacogenomics?

Pharmacogenomics studies how genetic differences affect the way people process medicines — how fast a drug is broken down, for example.

Think of it like…

different people metabolising caffeine at different rates. Same cup, different effect.

Why this matters to BharatGenome

The frequency of relevant variants differs between populations, so population-specific frequency data has direct research value here. BharatGenome reports frequencies only; it gives no clinical or dosing guidance.

5 · The representation problem

Everything above, pointed at the question BharatGenome exists to address.

What does population representation mean?

Population representation is about whose genomes are actually in the datasets that research depends on. A well-represented population is one whose diversity is genuinely captured.

Think of it like…

a national survey that mostly polled one region. The findings are real, but they describe that region best.

Why this matters to BharatGenome

This is the core problem statement. India's share of global genomic reference data is far smaller than its share of human genetic diversity.

What does transferability mean?

Transferability is whether a finding established in one population still holds in another. Many genomic findings transfer only partially.

Think of it like…

a recipe developed at sea level. It still works in the mountains, but not without adjustment.

Why this matters to BharatGenome

BharatGenome's comparison is a transferability check: does the global number describe the Indian population, or not?

Why can genomic findings behave differently across populations?

Because allele frequencies differ, LD patterns differ, and which variants were even measured differs. A method tuned on one population inherits all three assumptions.

Think of it like…

a spell-checker trained on one dialect. It is not broken — it is simply calibrated for someone else.

Why this matters to BharatGenome

It explains why this is a methodological issue with measurable consequences, not a matter of fairness alone.

Why does Indian genomic representation matter?

India holds a large share of humanity and a distinctive, highly structured pattern of genetic diversity shaped by its population history. That diversity is thinly covered in widely used reference resources.

many groupsdeep structurethin coverage
Think of it like…

a library with one wall of shelves left largely unfilled — you cannot tell what you are missing until you look.

Why this matters to BharatGenome

It is the reason BharatGenome makes Indian evidence the default side of every comparison rather than an optional filter.

How BharatGenome approaches this problem

BharatGenome puts Indian and global evidence side by side for the same query, explains the difference in plain language, links supporting literature, and states the provenance, confidence and limits of every figure. When a provider has no data, it says so instead of estimating.

Think of it like…

a second opinion printed next to the first, with both doctors' credentials attached.

Why this matters to BharatGenome

Making the gap visible and quantified is what turns a known problem into something a researcher can act on.

A note on scope

This section explains terminology so the comparison in Explore is readable without a genetics background. The 3D journey is a teaching visualisation: the molecular models are faithful educational abstractions rather than molecularly exact simulations, and every example number in it is labelled illustrative. It is educational material, not medical information, and none of it is diagnostic guidance.