Editing Karyotype (section)

=== Classic karyotype cytogenetics ===

[[File:PLoSBiol3.5.Fig7ChromosomesAluFish.jpg|thumb|Karyogram from a human female [[lymphocyte]] probed for the [[Alu sequence]] using [[Fluorescent in situ hybridization|FISH]]]]

In the "classic" (depicted) karyotype, a [[dye]], often [[Giemsa]] ''(G-banding)'', less frequently [[Mepacrine|mepacrine (quinacrine)]], is used to stain bands on the chromosomes. Giemsa is specific for the [[phosphate]] groups of [[DNA]]. Quinacrine binds to the [[adenine]]-[[thymine]]-rich regions. Each chromosome has a characteristic banding pattern that helps to identify them; both chromosomes in a pair will have the same banding pattern.

Karyotypes are arranged with the short arm of the chromosome on top, and the long arm on the bottom.  Some karyotypes call the short and long arms ''p'' and ''q'', respectively.  In addition, the differently stained regions and sub-regions are given numerical designations from [[Anatomical terms of location#Proximal and distal|proximal]] to [[Anatomical terms of location#Proximal and distal|distal]] on the chromosome arms.  For example, [[Cri du chat]] syndrome involves a deletion on the short arm of chromosome 5. It is written as 46,XX,5p-. The critical region for this syndrome is deletion of p15.2 (the [[locus (genetics)|locus]] on the chromosome), which is written as 46,XX,del(5)(p15.2).<ref>{{cite book|editor1=Lisa G. Shaffer |editor2=Niels Tommerup |title=ISCN 2005: An International System for Human Cytogenetic Nomenclature|publisher=S. Karger AG|location=Switzerland|isbn=978-3-8055-8019-9|year=2005}}</ref>