A derivative chromosome (der) is a structurally rearranged

chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are ...

generated either by a

chromosome rearrangement In genetics, a chromosomal rearrangement is a mutation that is a type of chromosome abnormality involving a change in the structure of the native chromosome. Such changes may involve several different classes of events, like deletions, duplicatio ...

involving two or more chromosomes or by multiple chromosome aberrations within a single chromosome (e.g. an inversion and a deletion of the same chromosome, or deletions in both arms of a single chromosome

The term always refers to the chromosome that has an intact centromere. Derivative chromosomes are designated by the abbreviation ''der'' when used to describe a

Karyotype A karyotype is the general appearance of the complete set of metaphase chromosomes in the cells of a species or in an individual organism, mainly including their sizes, numbers, and shapes. Karyotyping is the process by which a karyotype is disce ...

. The derivative chromosome must be specified in parentheses followed by all aberrations involved in this derivative chromosome. The aberrations must be listed from pter to qter and not be separated by a comma. For example, 46,XY,der(4)t(4;8)(p16;q22)t(4;9)(q31;q31) would refer to a derivative chromosome 4 which is the result of a translocation between the short arm of chromosome 4 at region 1, band 6 and the long arm of chromosome 8 at region 2, band 2, and a translocation between the long arm of chromosome 4 at region 3, band 1 and the long arm of chromosome 9 at region 3, band 1.

References

An International System for Human Cytogenetic Nomenclature, Shaffer, L.G., Tommerup N. (eds); S. Karger, Basel 2005 Chromosomes {{genetics-stub