The visual appearance of a chromosome when stained and examined under a microscope. Particularly important are visually distinct regions, called light and dark bands, which give each of the chromosomes a unique appearance. This feature allows a person's chromosomes to be studied in a clinical test known as a karyotype, which allows scientists to look for chromosomal alterations.

Dr. Eric Green, of the National Human Genome Research Institute's Genome Technology Branch, defines cytogenetic map.

Related terms: chromosome, deletion.