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Encyclopedia > Locus (genetics)
Short and long arms
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.
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
Example of bands

In biology and evolutionary computation, a locus is a fixed position on a chromosome, such as the position of a gene. A viable DNA coding at a given locus within a gene 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. Image File history File links Chromarms. ... Image File history File links Chromarms. ... From Nupedia File links The following pages link to this file: Chromosome Categories: GFDL images ... From Nupedia File links The following pages link to this file: Chromosome Categories: GFDL images ... A chromatid forms one part of a chromosome after it has coalesced for the process of mitosis or meiosis. ... The centromere is a region of chromosomes with a special sequence and structure. ... Image File history File links NF2. ... Image File history File links NF2. ... Biology (from Greek βίος λόγος, see below) is the branch of science dealing with the study of living organisms. ... In computer science evolutionary computation is a subfield of artificial intelligence (more particularly computational intelligence) involving combinatorial optimization problems. ... Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ... This stylistic schematic diagram shows a gene in relation to the double helix structure of DNA and to a chromosome (right). ... In genetics, an allele (pronounced al-eel) is any one of a number of viable DNA codings occupying a given locus (position) on a chromosome. ... In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ... A genetic map is a chromosome map of a species or experimental population that shows the position of its known genes and/or markers relative to each other, rather than as specific physical points on each chromosome. ... A genetic map refers to the assignment of DNA fragments to chromosomes. ... In biology, a trait or character is a feature of an organism. ...


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. Diploid (meaning double in Greek) cells have two copies (homologs) of each chromosome (both sex- and non-sex determining chromosomes), usually one from the mother and one from the father. ... Polyploid (in Greek: πολλαπλόν - multiple) cells or organisms contain more than one copy (ploidy) of their chromosomes. ... This article or section does not cite its references or sources. ... An organism is a heterozygote or heterozygous for a gene or trait if it has different alleles at the genes locus for each homologous chromosome. ...


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 "11q14-q21", 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. A microscope (Greek: (micron) = small + (skopein) = to look at) is an instrument for viewing objects that are too small to be seen by the naked or unaided eye. ... The centromere is a region of chromosomes with a special sequence and structure. ...


The ends of a chromosome are labeled "ptel" and "qtel", and so "2qtel" refers to the telomere of the long arm of chromosome 2. A telomere is a region of highly repetitive DNA at the end of a chromosome that functions as a disposable buffer. ...


External links

  • Overview at ornl.gov

  Results from FactBites:
 
Finch Genetics -FinchInfo.com- (1656 words)
The locus is the position that a given gene occupies on a chromosome.
The genotype or genetic makeup for this bird, therefore is single-factor for white breast, single-factor for purple breast.
The expression of a genotype in the appearance of an organism; the observed trait.
Locus - Wikipedia, the free encyclopedia (232 words)
Locus (genetics), the position of a gene (or other significant sequence) on a chromosome.
Locus (mathematics), the set of points satisfying a particular condition, often forming a curve of some sort.
In the classics, literature or theology, locus (or locus classicus) marks the first appearance of a phrase or the definitive passage that is authoritative for an idea.
  More results at FactBites »

 
 

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