The Principles of Clinical Cytogenetics - Extra Materials - Springer

Human Chromosome Nomenclature 57
nuc ish 13q14(Rb1x1)
Only one copy of the retinoblastoma locus probe Rb1 is detected. This implies a deletion of the Rb1 gene
from one chromosome 13.
nuc ish Yp11.2(DYZ3x2)
In this case, two copies of DYZ3 are detected, implying that an extra copy of this locus is present. It is not
clear whether the extra copy is the result of the presence of two Y chromosomes or an isochromosome
involving the short arm of the Y.
nuc ish 4cen(D4Z1x2),4p16.3(D4S96x1)
Here, we have an example of a structural abnormality identified with ish. Two copies of chromosome 4 are
implied by two D4Z1 signals. However, only one copy of D4S96 is detected, implying a deletion of this locus
from one chromosome 4. In the nomenclature, two or more probes for the same chromosome are separated by
commas.
nuc ish Xp22.3(STSx2),13q14(Rb1x3)
This is an example of ploidy detection. Two copies of the steroid sulfatase locus on the X chromosome
and three copies of the Rb1 locus are detected. This implies the presence of two X chromosomes and
trisomy 13. Probes from different chromosomes are separated by commas.
Designation of Relative Positions of the Signals
Under normal conditions, if probes from two chromosomes are tested simultaneously, the signals
are expected to appear separated. However, chromosome rearrangements, such as the BCR/ABL1
gene fusion, can bring signals together:
nuc ish 9q34(ABL1x2),22q11.2(BCRx2)
Two ABL1 and two BCR loci seen and they are well separated. No gene rearrangement is evident.
nuc ish 9q34(ABL1x2),22q11.2(BCRx2)(ABL1 con BCRx1)
Here, signals from two ABL1 and two BCR loci are seen. However, one ABL1 signal and one BCR signal are
juxtaposed (or connected, “con”), suggesting that they now reside on the same chromosome. This is the pattern
observed when a t(9;22) or “Philadelphia rearrangement” is present.