A specific position on a chromosome (plural: loci).
Use in clinical context
Knowing where in the genome a particular variant is found is important when examining the genomes of multiple individuals. This information ensures that each part of the genome is compared with the equivalent part in other individuals or reference genome. Loci are named according to convention. This can be by gene, position within a gene and location on the chromosome. For instance, the locus of the BRCA1 gene is the ‘q’ arm of chromosome 17 at position 21:31, written as 17q21:31.