chromosome constitution of a cell

The chromosome constitution of a cell is referred to as its
karyotype and there is an International System for Human
Cytogenetic Nomenclature (ISCN) for describing
abnormalities. The Paris convention in 1971 defined the
terminology used in reporting karyotypes. The centromere is
designated “cen” and the telomere (terminal structure of the
chromosome) as “ter”. The short arm of each chromosome is
designated “p” (petit) and the long arm “q” (queue). Each arm
is subdivided into a number of bands and sub-bands depending
on the resolution of the banding pattern achieved. High
resolution cytogenetic techniques have permitted identification
of small interstitial chromosome deletions in recognised
disorders of previously unknown origin, such as Prader–Willi
and Angelman syndromes. Deletions too small to be detected
by microscopy may be amenable to diagnosis by molecular
in situ hybridisation techniques.