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Locus (genetics)

 
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Locus (genetics)
 
 
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In the fields of genetics
Genetics

Genetics , a discipline of biology, is the science of heredity and Genetic variation in living organisms. The fact that living things inherit traits from their parents has been used since prehistoric times to improve crop plants and animals through selective breeding....
 and evolutionary computation
Evolutionary computation

In computer science evolutionary computation is a subfield of artificial intelligence that involves combinatorial optimization problems.Evolutionary computation uses iterative progress, such as growth or development in a population....
, a locus (plural loci) is a fixed position on a chromosome
Chromosome

A chromosome is an organized structure of DNA and protein that is found in Cell . A chromosome is a single piece of DNA that contains many genes, regulatory sequence and other genetic sequence....
 such as the position of a biomarker
Genetic marker

A genetic marker is a gene or DNA sequence with a known location on a chromosome and associated with a particular gene or trait. It can be described as a variation, which may arise due to mutation or alteration in the genomic loci, that can be observed....
 that may be occupied by one or more gene
Gene

A gene is the basic unit of heredity in a living organism. All living things depend on genes. Genes hold the information to build and maintain their cell and pass genetic trait to offspring....
s. A variant of the DNA sequence at a given locus is called an allele
Allele

An allele is one member of a pair or series of different forms of a gene. Usually alleles are coding region, but sometimes the term is used to refer to a junk DNA....
. The ordered list of loci known for a particular genome
Genome

In classical genetics, the genome of a diploid organism including eukarya refers to a full set of chromosomes or genes in a gamete; thereby, a regular somatic cell contains two full sets of genomes....
 is called a genetic map.






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Chromarms
In the fields of genetics
Genetics

Genetics , a discipline of biology, is the science of heredity and Genetic variation in living organisms. The fact that living things inherit traits from their parents has been used since prehistoric times to improve crop plants and animals through selective breeding....
 and evolutionary computation
Evolutionary computation

In computer science evolutionary computation is a subfield of artificial intelligence that involves combinatorial optimization problems.Evolutionary computation uses iterative progress, such as growth or development in a population....
, a locus (plural loci) is a fixed position on a chromosome
Chromosome

A chromosome is an organized structure of DNA and protein that is found in Cell . A chromosome is a single piece of DNA that contains many genes, regulatory sequence and other genetic sequence....
 such as the position of a biomarker
Genetic marker

A genetic marker is a gene or DNA sequence with a known location on a chromosome and associated with a particular gene or trait. It can be described as a variation, which may arise due to mutation or alteration in the genomic loci, that can be observed....
 that may be occupied by one or more gene
Gene

A gene is the basic unit of heredity in a living organism. All living things depend on genes. Genes hold the information to build and maintain their cell and pass genetic trait to offspring....
s. A variant of the DNA sequence at a given locus is called an allele
Allele

An allele is one member of a pair or series of different forms of a gene. Usually alleles are coding region, but sometimes the term is used to refer to a junk DNA....
. The ordered list of loci known for a particular genome
Genome

In classical genetics, the genome of a diploid organism including eukarya refers to a full set of chromosomes or genes in a gamete; thereby, a regular somatic cell contains two full sets of genomes....
 is called a genetic map. Gene mapping
Gene mapping

Genome mapping is the creation of a genetic map assigning DNA fragments to chromosomes.When a genome is first investigated, this map is nonexistent....
 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, heterozygous with respect to that gene.

Nomenclature

The chromosomal locus of a gene might be written "6p21.3".

Component Explanation >- 1.2 | 6 - | p p for petit in French); q indicates the long arm. >- 5.6 | 21.3 The numbers that follow the letter represent the position on the arm: band 21, sub-band 3. The bands are visible under a microscope
Microscope

A microscope is an Laboratory equipment for viewing objects that are too small to be seen by the naked or unaided eye. The science of investigating small objects using such an instrument is called microscopy....
 when the chromosome is suitably stained
G banding

G-banding is technique used in cytogenetics to produce a visible karyotype by staining condensed chromosomes. The metaphase chromosomes are treated with trypsin and Staining with Giemsa....
. Each of the bands is numbered, beginning with 1 for the band nearest the centromere
Centromere

A centromere is a region of DNA typically found near the middle of a chromosome where two sister chromatids come in contact. It is involved in cell division as the point of mitotic spindle....
. 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
OCA1

Oculocutaneous Albinism Type 1 is the gene associated with albinism, an autosomal recessive disorder. Albinism occurs when something causes the OCA1 gene to function improperly....
 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
Telomere

A telomere is a region of repetitive DNA at the end of chromosomes, which protects the end of the chromosome from destruction. Its name is derived from the Greek nouns telos "end" and mer?s "part"....
 of the long arm of chromosome 2.

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