Homogeneously staining regions (HSRs) are chromosomal segments with various lengths and uniform staining intensity after

G banding G-banding, G banding or Giemsa banding is a technique used in cytogenetics to produce a visible karyotype by staining condensed chromosomes. It is the most common chromosome banding method. It is useful for identifying genetic diseases through t ...

. This type of aberration is also known as Copy Number Gains or Amplification. An HSR is one type of change in a

chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are ...

's structure which is frequently observed in the

nucleus Nucleus ( : nuclei) is a Latin word for the seed inside a fruit. It most often refers to: *Atomic nucleus, the very dense central region of an atom * Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA Nucl ...

of human

cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...

cells. In the region of a chromosome where an HSR occurs, a segment of the chromosome, which presumably contains a

gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...

or genes that give 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 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

* * An International System for Human Cytogenetic Nomenclature, Shaffer, L.G., Tommerup N. (eds); S. Karger, Basel 2005 Chromosomes Cancer {{genetics-stub