“Cytogenetics traditionally refers to the study of chromosomes by microscopy following the application of banding techniques, permitting identification of abnormalities of chromosome number, loss or gain of chromosomal material or positional changes”. Standardized nomenclature is critical for the accurate and consistent description of genomic changes as identified by karyotyping, fluorescence in situ hybridization and microarray. The International System for Human Cytogenomic Nomenclature (ISCN) is the central reference for the description of karyotyping, FISH, and microarray results, and provides rules for describing cytogenetic and molecular cytogenetic findings in laboratory reports. These laboratory reports are documents to the referring clinician, and should be clear, accurate and contain all information relevant for good interpretation of the cytogenetic findings.

1. Cytogenetic Nomenclature &
Abbreviations
By:
Manahil khanum
(B-MMG-17-42)

2. Cytogenetics
Cytogenetics traditionally refers to the study of
chromosomes by microscopy following the
application of banding techniques, permitting
identification of abnormalities of chromosome
number, loss or gain of chromosomal material or
positional changes.

3. 3
THE NORMAL HUMAN KARYOTYPE
p (petit) pter for the short
arm and q qter for the
long arm
The International
System for Human
Cytogenetic
Nomenclature (ISCN)
was
established in 1978.
A normal human karyotype contains 23 pairs of chromosomes: 22 pairs of autosomes and 1 pair of sex chromosomes, generally
arranged in order from largest to smallest. A karyotype can be used to visualize abnormalities in the chromosomes, such as an
incorrect number of chromosomes, deletions, insertions, or translocations of DNA.
The main landmarks of each
chromosome are the
centromere, cen,
Satellite chromosomes or SAT-
chromosomes are chromosomes th
at contain secondary constructs that
serve as identifying markers. In
addition to the centromere, one or
more secondary constrictions can be
observed in some chromosomes at
metaphase.
These chromosomes are
called satellite chromosomes.
Any subdivision of
a chromosome along its length.
Chromosomal regions include parts
that are not part of the chromatin
.Each region is further subdivided into
bands and subands.

4. 4
BANDS & SUB BANDS
Chromosome banding refers to alternating light
and dark regions along the length of
a chromosome, produced after staining with a
dye.
A band is defined as the part of
a chromosome that is clearly distinguishable from
its adjacent segments by appearing darker or
lighter with the use of one or more banding
techniques.
To clarify more the study of chromosome(position)
Sub bands which are Sub divisions of bands are
used.
The cytogenetic bands are labeled p1, p2, p3,
q1, q2, q3, etc., counting from the centromere
out toward the telomeres. ... The sub-bands are
also numbered from the centromere out toward
the telomere.

5. 5
How to Write Karyotypes
Place a comma behind the
first number. This is
followed by identifying
the sex chromosomes XX
(female) or XY (male),
write the appropriate sex.
(eg. 46,XX is female; 46, XY
is male)
Match the homologous
chromosomes according to
their size (descending
order), centromere position
and banding pattern. These
three indicators will serve
as a guide for properly
matching the chromosomes
creating your karyotype..
Write the total number of
chromosomes for the test
subject used (humans, dogs,
pigs. etc. have different
numbers of chromosomes).
For people the number is 46,
unless there are defective or
additional chromosomes.
Add a plus or minus sign to the
affected chromosome number for an
abnormal karyotype, placing it
behind a comma after the sex
chromosome. The plus or minus sign
signifies there is an added
chromosome or missing
chromosome (or a chromosome can
be missing parts). For a male with an
extra number 19 chromosome, the
karyotype would be displayed as
47,XY,+19 as one chromosome was
added to the total of 46; +19 is
displayed at the end, identifying the
additional chromosome.

6. 6
How to Write Karyotypes
Make another set of
parenthesis directly after
the first set of parenthesis.
Within the parenthesis
write a 'p' for the short arm
of the chromosome or a 'q'
for the long arm. This
establishes which part (or
arm) of the chromosome is
missing.
Add (or subtract) one to or
from your total number in
the first set of numbers for
the abnormal karyotype. If
there is only a part of the
chromosome missing or
added, the first set of total
numbers will not be
affected.
Write 'del' when a
chromosome is missing only
parts. Del is written in a third
set of numbers (replacing the
plus and minus sign and
affected chromosome)
before a set of parenthesis.
Within the parenthesis write
the number of the affected
chromosome incurring
change.
Find the 'break point' of the change
indicating the chromosome in the
second set of parenthesis. Put the p
or q before the break point
chromosome. Example, a female
missing the bottom arm of a
chromosome 5 would be expressed
as 46,XX, del(5)(q16). 'Del' says the
chromosome is missing something.
(5) delineates the origin of the
problem. 'Q' indicates the missing
part of the chromosome is the long
arm. '16' identifies the break point
chromosome.

7. 7
Cytogenetic Nomenclature
Abbreviation Meaning Example Condition
46, XX Normal Female Karyotype
46, XY Normal Male Karyotype
cen Centromere
del Deletion 46,XX,del(5p)
Female with cri du chat syndrome due to
deletion of part of short arm of one
chromosome 5
der derivative chromosome der(1)
Translocation chromosome derived from
chromosome 1 and containing the centromere
of chromosome 1
dic dicentric chromosome dic(X;Y)
Translocation chromosome containing
centromeres from both the X and the Y
chromosomes
dup Duplication
fra fragile site 46, Y fag(X)(q27.3) Male with fragile X chromosome
i isochromosome 46,X,i(Xq)
Female with isochromosome fro the long arm
of the X chromosome.
ins Insertion
inv Inversion inv(3)(p25:q21) Pericentric inversion of chromosome 3
mar marker chromosome 47,XX,+mar
Female with an extra unidentified
chromosome.

8. 8
mat maternal origin 47,XY,der(1)mat
male with additional der(1) translocation
chromosome inherited from his mother.
p short arm of chromosome
pat paternal origin
q long arm of chromosome
r ring chromosome 46,X,r(X) Female with ring X chromosome
rcp reciprocal translocation
rob Robertsonian translocation
t Translocation 46,XX,t(2;8)(q21;p13)
Female with balanced translocation between
chromosome 2 and chromosome 8, with breaks in
2q21 and 8p13
ter Terminus 46, X,Xq-(pter-->q21:)
Female with partial deletion of the long arm from
Xq21 to Xqter (nomenclature shows the portion
of the chromosome that is present)
+ gain of 47,XX,+21 Female with trisomy 21
- loss of 45,XX,-14,-21,+t(14q21q)
Normal female carrier of a robertsonian
translocation between the long arms of
chromosomes 14 and 21; karyotype is missing a
normal 14 and a normal 21
4p-
Chromosome 4 with a on of the short
arm deleted.
: Break 5qter -->5p15:
deleted chromosome 5 in a patient with cri du
chat syndrome, with a deletion breakpoint in band
p15
:: break and join 2pter-->2q21::8p13-->8pter Description of der(2) portion of t(2,8)
/ Mosaicism 46,XX/47,XX,+8
Female with two populations of cells, a normal
karyotype and one with trisomy 8
Cytogenetic Nomenclature

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