Locus (genetics)

In and, a locus (plural loci) is a fixed position on a , such as the position of a  or a biomarker. A variant of the DNA sequence at a given locus is called an. The ordered list of loci known for a particular is called a. is the process of determining the locus for a particular.

and cells whose chromosomes have the same allele at some locus are called, while those that have different alleles at a locus,.

Nomenclature
The chromosomal locus of a gene might be written "6p21.3".

A range of locations is specified in a similar way. For example, the locus of gene may be written "11q1.4-q2.1", meaning it is on the long arm of chromosome 11, somewhere in the range of sub-band 4 of band 1, and sub-band 1 of band 2.

The ends of a chromosome are labeled "ptel" and "qtel", and so "2qtel" refers to the of the long arm of chromosome 2.