locus the specific point on a chromosome where the gene is found Source: Jenkins, John B. 1990. Human Genetics, 2nd Edition. New York: Harper & Row ... A locus (plural loci), in genetics, is the specific location or position of a gene, DNA sequence, on a chromosome. Each chromosome carries many genes; humans' estimated 'haploid' protein coding genes are 20,000-25,000, on the 23 different chromosomes. [en.wikipedia.org/wiki/Locus_(genetics)]