Loci

Loci is the plural of locus, a term with different but related meanings in mathematics, genetics, and other fields. In mathematics, a locus is the set of all points that satisfy a given condition. For example, the locus of points at a fixed distance from a fixed point is a circle; the locus of points equidistant from a fixed point and a fixed line is a parabola. More generally, a locus is described by equations or inequalities that define a subset of a space.

In genetics, a locus is the specific position on a chromosome where a gene or genetic marker resides. Loci on chromosomes are used to describe where genes are located, with alleles representing variant forms at a locus. Genetic linkage studies and genome-wide association studies map loci to understand how traits and diseases are inherited. A disease locus refers to a chromosomal region linked to a particular phenotype, which may contain one or more causal genes.

Across disciplines, the concept of a locus emphasizes a defined place or set of points that meet criteria, often forming a curve, surface, or region in mathematics or a physical location on a chromosome in genetics.