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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. 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. 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.〔(【引用サイトリンク】url=http://www.cancer.gov/geneticsdictionary?expand=H )〕 == Nomenclature == The chromosomal locus of a gene might be written "6p21.3". Because "21" refers to "region 2, band 1" this is read as "two one", not as "twenty-one". So the entire locus is "six P two one point three." A range of loci is specified in a similar way. 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. The ends of a chromosome are labeled ''"pter"'' and ''"qter"'', and so ''"2qter"'' refers to the terminus of the long arm of chromosome 2. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Locus (genetics)」の詳細全文を読む スポンサード リンク
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