# Genome builds: GRCh38 versus hg19 (GRCh37)

Source: https://onco.cc/terms/genome-builds/  
OnCo record `genome-builds` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

A genome build is the version of the human reference sequence coordinates are measured against; mixing GRCh38 and the older hg19 puts variants at the wrong positions.

## Summary

A reference genome is an assembly representing an organism's complete genetic sequence as a continuous string, accompanied by annotation (Wikipedia). GRCh38 (hg38), released in 2013, is the current human reference; GRCh37 (hg19) preceded it and much legacy TCGA data was aligned to it before the GDC re-harmonised everything to GRCh38. Coordinates differ between builds, so files must be lifted over or re-aligned, and the build is a mandatory provenance field.

## Fields

- Kind: Term
- Last checked: 2026-09-24
- Also known as: GRCh38; hg38; hg19; GRCh37; genome build; reference build; reference genome build; liftover
- Tags: cansim-terms

## Notes

- Listed in the CanSim terms map 1.0.0 (docs/onco/terms.json, generated 2026-09-24), CC BY 4.0, attribution: CanSim project, an open, public-data-first cancer foundation-model programme; CanSim page path /terms/grch38-vs-hg19.

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Reference_genome
- GRCh38.p14 assembly at NCBI Datasets: https://www.ncbi.nlm.nih.gov/datasets/genome/GCF_000001405.40/
- Wikipedia: https://en.wikipedia.org/wiki/Reference_genome

## Connected records

- terms: [Cancer AI vocabulary (CanSim terms map)](https://onco.cc/terms/cancer-ai-vocabulary/), [Ensembl gene ID](https://onco.cc/terms/ensembl-gene-id/), [HGNC gene symbol](https://onco.cc/terms/hgnc-symbol/), [HGVS variant nomenclature](https://onco.cc/terms/hgvs/), [Provenance fields for research data](https://onco.cc/terms/provenance-fields/), [STAR and Salmon (RNA-seq alignment and quantification)](https://onco.cc/terms/star-salmon/), [Variant calling](https://onco.cc/terms/variant-calling/)

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JSON: https://onco.cc/api/v1/entities/genome-builds.json