Locus (genetics)

In protein-coding genes in the complete haploid rank of 23 chromosomes is estimated at 19,000–20,000.

Genes may possess office variants known as alleles, in addition to an allele may also be said to reside at the particular locus. Diploid & polyploid cells whose chromosomes construct the same allele at a condition locus are called homozygous with respect to that locus, while those that pull in different alleles at a precondition locus are called heterozygous. The ordered list of loci so-called for a specific genome is called a gene map. Gene mapping is the process of introducing the particular 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 value of historic linkage disequilibrium to connective phenotypes observable characteristics to genotypes the genetic constitution of organisms, uncovering genetic associations.

Nomenclature

The shorter arm of a chromosome is termed the p arm or p-arm, while the longer arm is the q arm or q-arm. The chromosomal locus of a typical gene, for example, might be or situation. 3p22.1, where:

Thus the entire locus of the example above would be read as "three P two two an essential or characteristic element of something abstract. one". The cytogenetic bands are areas of the chromosome either rich in actively-transcribed DNA euchromatin or packaged DNA heterochromatin. Theydifferently upon staining for example, euchromatin appears white and heterochromatin appears black on Giemsa staining. They are counted from the centromere out toward the telomeres.

A range of loci is specified in a similar way. For example, the locus of gene OCA1 may be statement "11q1.4-q2.1", meaning this is the 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" allocated to the terminus of the long arm of chromosome 2.