Definition of Chromosome band

Chromosome band: One of the transverse bands produced on chromosomes by differential staining techniques. Depending on the particular staining technique, the bands are alternating light and dark or fluorescent and nonfluorescent.

Each human chromosome has a short arm ("p" for "petit") and long arm ("q" for "queue") separated by a centromere. The ends of the chromosome are called telomeres.

Each chromosome arm is divided into regions, or cytogenetic bands, that can be seen using a microscope and special stains. The cytogenetic bands are labeled p1, p2, p3, q1, q2, q3, etc., counting from the centromere out toward the telomeres. At higher resolutions, sub-bands can be seen within the bands. The sub-bands are also numbered from the centromere out toward the telomere.

For example, the cytogenetic map location of a gene termed CFTR (cystic fibrosis transmembrane conductance regulator) is 7q31.2, which indicates it is on chromosome 7, q arm, band 3, sub-band 1, and sub-sub-band 2.

The ends of the chromosomes are labeled ptel and qtel. For example, the notation 7qtel refers to the telomere (the end) of the long arm of chromosome 7.