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
approximate sign (~) denotes intervals and boundaries of a chromosome segment or number of chromosomes, fragments, or markers; denotes a range of number of copies of a chromosomal region when the exact number cannot be determined
arr microarray
arrow (-> or →) from - to, in detailed system
brackets, square ([ ]) surround number of cells or genome build
cen centromere
cgh comparative genomic hybridization
chr chromosome
cht chromatid
colon, single (:) break, in detailed system
colon, double (::) break and reunion, in detailed system
comma (,) separates chromosome numbers, sex chromosomes, and chromosome abnormalities, seperates locus designations
cp composite karyotype
decimal point (.) denotes sub-bands
del deletion
der derivative chromosome
dic dicentric
dn designates a chromosome abnormality that has not been inherited (de novo)
dup duplication
fra fragile site
h heterochromatin, constitutive
hmz homozygous, homozygosity; used when one or two copies of a genome are detected, but previous, known heterozygosity has been reduced to homozygosity through a variety of mechanisms, e.g. loss of heterozygosity (LOH)
hsr homogeneously staining region
htz heterozygous, heterozygosity
i isochromosome
idic isodicentric chromosome
ins insertion
inv inversion
mar marker chromosome
mat maternal origin
mos mosaic
p short arm of chromosome
parentheses ( ) surround structurally altered chromosomes and breakpoints; surround chromosome numbers, X, and Y in normal and abnormal results; surround coordinates (or nucleotide positions) in abnormal result
pat paternal origin
ps satellited short arm of chromosome
pter terminal end of the short arm
q long arm of chromosome
qter terminal end of the long arm
question mark (?) questionable identification of a chromosome or chromosome structure
r ring chromosome
rec recombinant chromosome
rob robertsinian translocation
s satellite
sce sister chromatid exchange
sdl sideline
seq sequencing
slant line, single (/) separates clones, or contiguous probes
stk satellite stalk
subtel subtelomeric region
t translocation
tas telomeric association
ter terminal (end of chromsome) or telomere
upd uniparental disomy
var variant or variable region

In Situ Hybridization: Symbols and Abbreviations

minus sign (-) loss; decrease in length; locus absent from a specific chromosome
plus sign, single (+) additional normal or abnormal chromosomes; increase in length locus present on a specific chromosome
plus sign, double (++) two hybridization signals or hybridization regions on a specific chromosome
multiplication sign (x) multiple copies of rearranged chromosomes; designates aberrant polyploidy clones in neoplasias; with number to indicate number of signals seen; multiple copies of a chromosome or chromosomal region
period (.) separates various techniques
semicolon (;) separates altered chromosomes and breakpoints in structural rearrangements involving more than one chromosome; seperates probes on different derivative chromosomes
FISH fluorescence in situ hybridization
ish in situ hybridization; when used without a prefix applies to metaphase or prometaphase chromosomes of dividing cells
wcp whole chromosome paint