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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. [ 1 ] It is useful for identifying genetic diseases (mainly chromosomal abnormalities ) through the photographic representation of the entire chromosome ...
High-resolution banding involves the staining of chromosomes during prophase or early metaphase (prometaphase), before they reach maximal condensation. Because prophase and prometaphase chromosomes are more extended than metaphase chromosomes, the number of bands observable for all chromosomes ( bands per haploid set , bph; "band level ...
Chromosomes at various stages of mitosis.Karyograms are generally made by chromosomes in prometaphase or metaphase. During these phases, the two copies of each chromosome (connected at the centromere) will look as one unless the image resolution is high enough to distinguish the two.
These techniques produce a characteristic pattern of contrasting dark and light transverse bands on the chromosomes. Banding makes it possible to identify homologous chromosomes and construct chromosomal nomenclatures for many species. Banding of homologous chromosomes allows chromosome segments and rearrangements to be identified.
G-banding patterns of human chromosome 12 in three different resolutions (400, [12] 550 [13] and 850 [3]). Band length in this diagram is based on the ideograms from ISCN (2013). [ 14 ] This type of ideogram represents actual relative band length observed under a microscope at the different moments during the mitotic process .
As of 2006, even high-resolution CGH arrays are accurate to detect structural variations (SV) at resolution of 200 bp. [16] This method allows one to identify new recurrent chromosome changes such as microdeletions and duplications in human conditions such as cancer and birth defects due to chromosome aberrations. Figure 2.
G-banding patterns of human chromosome 6 in three different resolutions (400, [15] 550 [16] and 850 [3]). Band length in this diagram is based on the ideograms from ISCN (2013). [ 17 ] This type of ideogram represents actual relative band length observed under a microscope at the different moments during the mitotic process .
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