<P> A locus (plural loci) in genetics is a fixed position on a chromosome, like the position of a gene or a marker (genetic marker). Each chromosome carries many genes; human's estimated' haploid' protein coding genes are 19,000 - 20,000, on the 23 different chromosomes . A variant of the similar DNA sequence located at a given locus is called an allele . The ordered list of loci known for a particular genome is called a gene map . Gene mapping is the process of determining the locus for a particular biological trait . </P> <P> Diploid and polyploid cells whose chromosomes have the same allele of a given gene at some locus are called homozygous with respect to that gene, while those that have different alleles of a given gene at a locus are called heterozygous with respect to that gene . </P>

Where is the gene located in the chromosome