Everything about Locus Genetics totally explained
In
biology and
evolutionary computation, a
locus (plural
loci) is a fixed position on a
chromosome, such as the position of a
gene or a biomarker (
genetic marker). 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.
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's 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.
Further Information
Get more info on 'Locus Genetics'.
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