View source for Biology:Homogeneously staining region

'''Homogeneously staining regions''' ('''HSRs''') are chromosomal segments with various lengths and uniform staining intensity after [[Biology:G banding|G banding]]. This type of [[Biology:Chromosome abnormality|aberration]] is also known as Copy Number Gains or Amplification.
An HSR is one type of change in a [[Biology:Chromosome|chromosome]]'s structure which is frequently observed in the [[Biology:Cell nucleus|nucleus]] of human [[Medicine:Cancer|cancer]] [[Biology:Cell|cells]]. In the region of a chromosome where an HSR occurs, a segment of the chromosome, which presumably contains a [[Biology:Gene|gene]] or genes that give [[Biology:Fitness|selective advantage]] to the progression of the cancer, is amplified or duplicated many times.  As a result of the duplication this chromosomal segment is greatly lengthened and expanded such that when it is stained with a [[Biology:Hybridization probe|fluorescent probe]] specific to the region (Fluorescent in situ hybridization), rather than causing a focal fluorescent signal as in a normal chromosome, the probe "paints" a broad fluorescent signal over the whole of the amplified region.  It is because of the appearance of this broadly staining region that this chromosomal abnormality was named a homogeneously staining region. The homogenously staining region was first observed in chromosome 2 by June Biedler  and Barbara Spengler in cells that had been made resistant to methotrexate.  The HSR was found to due to the amplification of the DHFR gene. 

==References==
* {{cite journal |author=Biedler JL |author2=Spengler BA |title=Metaphase chromosome anomaly: association with drug resistance and cell-specific products |journal=Science |volume=191 |issue=4223 |date=1976-01-16 |pages=185–187 |doi=10.1126/science.942798 |pmid=942798 |bibcode=1976Sci...191..185B }}
* An International System for Human Cytogenetic Nomenclature, Shaffer, L.G., Tommerup N. (eds); S. Karger, Basel 2005

[[Category:Chromosomes]]
[[Category:Cancer]]



{{Sourceattribution|Homogeneously staining region}}