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.
- Chromosome banding
Chromosome banding: The treatment of chromosomes to reveal characteristic patterns of horizontal bands like bar codes. The banding patterns lend each chromosome a distinctive appearance so the 22 pairs of human nonsex chromosomes and the X and Y chromosomes can be identified and distinguished without ambiguity. Banding also permits the recognition of chromosome deletions (lost […]
- Chromosome complement
Chromosome complement: The whole set of chromosomes for a species. In humans, the normal chromosome complement consists of 46 chromosomes, including the 2 sex chromosomes. Also known as the karyotype.
- Chromosome disorder
Chromosome disorder: An abnormal condition due to something unusual in an individual’s chromosomes. For example, Down syndrome is a chromosome disorder caused by the presence of an extra copy of chromosome 21, and Turner syndrome is most often due to the presence of only a single sex chromosome: one X chromosome.
- Chromosome duplication
Chromosome duplication: Part of a chromosome in duplicate. A particular kind of mutation involving the production of one or more copies of any piece of DNA, including sometimes a gene or even an entire chromosome. A duplication is the opposite of a deletion. Duplications have been important in the evolution of the human genome (and […]
- Chromosome inversion
Chromosome inversion: A condition in which a chromosome segment is clipped out, turned upside down, and reinserted back into the chromosome. A chromosome inversion can be inherited from one or both parents, or it may be a mutation that appears in a child whose family has no history of chromosome inversion. An inversion can be […]