ISCN Symbols and Abbreviated Terms

Symbols and abbreviated terms used in the description of chromosomes and chromosomal abnormalities are listed below. For a detailed discussion of these terms, consult ISCN (1995): An International System for Human Cytogenetic Nomenclature, Mitelman, F (ed); S. Karger, Basel, 1995.

Consider the following when searching for chromosomal abnormalities:

add additional material of unknown origin
arrow (->) from - to, in detailed system
brackets, square ([]) surround the number of cells
cen centromere
colon, single (:) break, in detailed system
colon, double (::) break and reunion, in detailed system
comma (,) separates chromosome numbers, sex chromosomes, and chromosome abnormalities
decimal point (.) denotes sub-bands
del deletion
de novo designates a chromosome abnormality which has not been inherited
der derivative chromosome
dic dicentric
dup duplication
fra fragile site
h heterochromatin, constitutive
hsr homogeneously staining region
i isochromosome
ins insertion
inv inversion
mar marker chromosome
mat maternal origin
minus sign (-) loss
p short arm of chromosome
parentheses surround structurally altered chromosome and breakpoints
pat paternal origin
plus sign (+) gain
q long arm of chromosome
question mark (?) questionable identification of a chromosome or chromosome structure
r ring chromosome
rec recombinant chromosome
s satellite
sce sister chromatid exchange
semicolon (;) separates altered chromosomes and breakpoints in structural rearrangements involving more than one chromosome
slant line (/) separates clones
t translocation
ter terminal (end of chromsome)
upd uniparental disomy

In Situ Hybridization: Symbols and Abbreviations

minus sign (-) absent from a specific chromosome
plus sign (+) present on a specific chromosome
multiplication sign (x) precedes the number of signals seen
period (.) separates cytogenetic observations from results of in situ hybridization
semicolon (;) separates probes on different derivative chromosomes
fish fluorescence in situ hybridization
ish in situ hybridization; when used without a prefix applies to chromsomes (usually metaphase or prometaphase) of dividing cells
wcp whole chromosome paint