G-banding or Giemsa bandings is a technique used in cytogenetics to produce a visible karyotype by staining condensed chromosomes . It is useful for identifying genetic diseases through photographic representation of the entire chromosomal complement .  Metaphase chromosomes are treated with trypsin (to partially digest the chromosome) and stained with Giemsa stain . heterochromatic region consisting of adenine and thymineare richStain more deeply in (AT-rich) DNA and relatively gene-poor, G-bandings. In contrast, less condensed chromatin ( euchromatin ) —which is enriched with guanine and cytosine ( GC-rich ) and is more transcriptionally active—incorporates less Giemsa stain , and these regions tend to be lighter bands in G-bandings. appear as. The patterns of bands are numbered on each arm of the chromosome from telomere to centromere . This numbering system allows any band on the chromosome to be identified and accurately described. The reverse of Gbands is achieved in R‑banding . Bandings can be used to identify chromosomal abnormalities, such as translocations , as there is a unique pattern of light and dark bands for each chromosome.
It is difficult to identify and group chromosomes based on simple staining because the uniform color of the structures then makes it possible to differentiate between different chromosomes. Therefore, techniques such as G‑banding have been developed that allow “bands” to appear on chromosomes. These bands were similar in appearance to homologous chromosomes , thus, making identification easier and more accurate. The less condensed chromosomes are, the more bands appear during G-bandings. This means that different chromosomes differ more in prophase than in metaphase.
Other types of cytogenic bandings are listed below:
|Banding Type||blur method|
|g banding||Giemsa stain|
|r-banding||reverse Giemsa staining|