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A derivative chromosome (der) is a structurally rearranged
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
A derivative chromosome (der) is a structurally rearranged chromosome
A chromosome is a package of DNA containing part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most import ...
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 Deletion (genetics), d ...
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 chromosomeThe 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 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 discerned by de ...
. 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. As for the initial string "46,XY", it only signifies that this translocation is occurring in an organism, which has this set of chromosomes, i.e. a human being.
References
An International System for Human Cytogenetic Nomenclature, Shaffer, L.G., Tommerup N. (eds); S. Karger, Basel 2005 Chromosomes {{genetics-stub