Karyotype Nomenclature
A karyotype is described by an abbreviation containing the total number of chromosomes, a comma, and the sex chromosomes of an individual. If the individual carries a chromosomal abnormality, this can be described in the karyotype abbreviation. As a general rule, only abnormalities are indicated in a karyotype (apart from the total number of chromosomes and the sex chromosomes).
The nomenclature of band assignment and chromosome aberration is according to the International System for Human Cytogenetic Nomenclature (ISCN).
Symbol used in designing karyotypes
| Symbol | Description | |
|---|---|---|
| 1-22 | Autosome | |
| X,Y | Sex chromosome | |
| (+) or (-) | When placed before an autosomal number, this indicates that the chromosome is an extra or is missing | |
| cen | Centromere | |
| inv | Inversion | |
| dic | Dicentric | |
| p | Short arm of the chromosome | |
| q | Long arm of the chromosome | |
| t | Translocation | |
| del | Deletion | |
| ins | Insertion | |
| dup | Duplication | |
| ter | Terminal | |
| der | Derivative | |
| : | Break | |
| :: | Break and join | |
| → | From to |
Examples of karyotype abbreviations:
| Symbol | Description | |
|---|---|---|
| 46,XY | Normal male chromosome constitution | |
| 47,XX,+21 | Female with trisomy 21, i.e. Down syndrome | |
| 47,XY,+21(10)/46,XY(10) | Male who is a mosaic of trisomy 21 cells and normal cells (10 cells scored for each karyotype) | |
| 46,XY,del(4)(p14) | Male with a deletion of the short arm of chromosome 4 from the band designated 14 to the telomere | |
| 46,XX,dup(5)(p14p15.3) | Female with a duplication of the short arm of chromosome 5 from bands p14 to p15.3 | |
| 45,XY,der(13;14)(q10;q10) | A male with a balanced Robertsonian translocation of chromosomes 13 and 14. The karyotype shows that one normal 13 and one normal 14 are missing and replaced with a derivative chromosome | |
| 46,XY,t(11;22)(q23;q22) | A male with a balanced reciprocal translocation between chromosomes 11 and 22. The breakpoints are at 11q23 and 22q22 | |
| 46,XX,inv(3)(p21;q13) | An inversion on chromosome 3 that extends from p21 to q13; because it includes the centromere, this is a pericentric inversion | |
| 46,X,r(X) | A female with one normal X chromosome and one ring X chromosome | |
| 46,X,i(Xq) | A female with one normal X chromosome and an isochromosome of the long arm of the X chromosome |