explain cytogenetic bands

[zhangxiaobo]

I have a question about cytogenetic bands,I hope someone tell me what is cytogenetic bands and how to understand this noun well.
Thank you very much!
All best.

[ulz_peter]

Hi zhangxiaobo,

When chromosomes are stained (with for example Giemsa) in the metaphasis of mitosis the different chromosomes get stained according to their content of GC creating darker spots and whiter spots. These techniques are called Cytogenetics and are used to observe large genetic aberrations, like trisomies, large duplications/insertions/deletions/translocations and triploidies.

These different shadings are called bands each having a specific number e.g. 7p2.3 which is on the short arm of chromosome 7, the band 2, subband 3.

They are rarely used in molecular genetics but can serve as landmarks on chromosomes for orientation.

Hope that helps,

[ECO]

Thanks for answering this somewhat off topic question ulz_peter!

[malachig]

Adding to the excellent description of ulz_peter. You can determine the cytogenetic band (also known as chromosome band) that corresponds to a particular gene or chromosome coordinate at the UCSC genome browser. For example, for human:
http://genome.ucsc.edu/cgi-bin/hgGateway

Under 'Mapping and Sequencing Tracks' is a track called 'Chromosome Band'. If you click on the name of this track, UCSC provides an excellent description:

"The chromosome band track represents the approximate location of bands seen on Giemsa-stained chromosomes. Chromosomes are displayed in the browser with the short arm first. Cytologically identified bands on the chromosome are numbered outward from the centromere on the short (p) and long (q) arms. At low resolution, bands are classified using the nomenclature [chromosome][arm][band], where band is a single digit. Examples of bands on chromosome 3 include 3p2, 3p1, cen, 3q1, and 3q2. At a finer resolution, some of the bands are subdivided into sub-bands, adding a second digit to the band number, e.g. 3p26. This resolution produces about 500 bands. A final subdivision into a total of 862 sub-bands is made by adding a period and another digit to the band, resulting in 3p26.3, 3p26.2, etc."

[zhangxiaobo]

Thanks for your answer.It make me understand this clearly.

[ulz_peter]

I can't compete with the UCSC Team...