LOCUS (GENETICS)

Short and long arms

Chromosome.
(1) Chromatid. One of the two identical parts of the chromosome after S phase.
(2) Centromere. The point where the two chromatids touch, and where the microtubules attach.
(3) Short arm
(4) Long arm.

Example of bands

In biology and evolutionary computation, a 'locus' (plural 'loci') is a fixed position on a chromosome, such as the position of a gene. A variant of the DNA sequence at a given locus is called an allele. The ordered list of loci known for a particular genome is called a genetic 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 at some locus are called homozygous, while those that have different alleles at a locus, heterozygous.

Contents
Nomenclature
External links

Nomenclature


The chromosomal locus of a gene might be written "6p21.3".
'Component' 'Explanation'
''6'' The chromosome number.
''p'' The position is on the chromosome's short arm (''p'' for ''petit'' in French); ''q'' indicates the long arm.
''21.3'' The numbers following the letter represent the position on the arm: band 21, sub-band 3. The bands are visible under a microscope when the chromosome is suitably stained. Each of the bands is numbered, beginning with 1 for the band nearest the centromere. Sub-bands and sub-sub-bands are visible at higher resolution.

A range of locations 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 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 telomere of the long arm of chromosome 2.

External links



★ Overview at ornl.gov

This article provided by Wikipedia. To edit the contents of this article, click here for original source.

psst.. try this: add to faves
©2009 TripAtlas.com