Locus (genetics)

: loci) is a specific, fixed position on a chromosome where a particular gene or genetic marker is located.

[3] The ordered list of loci known for a particular genome is called a gene map.

Gene mapping is the process of determining the specific locus or loci responsible for producing a particular phenotype or biological trait.

Association mapping, also known as "linkage disequilibrium mapping", is a method of mapping quantitative trait loci (QTLs) that takes advantage of historic linkage disequilibrium to link phenotypes (observable characteristics) to genotypes (the genetic constitution of organisms), uncovering genetic associations.

For example, the locus of gene OCA1 may be written "11q1.4-q2.1", meaning it is on the long arm of chromosome 11, somewhere in the range from sub-band 4 of region 1 to sub-band 1 of region 2.