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Sarwat MaroofSenior. Technologist
Cytogenetics section
Histopathology
AGA KHAN UNIVERSITY HOSPITAL
HUMAN
KARYOTYPING
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What is cytogenetics?
The study of chromosomes and the related
disease states caused by abnormal chromosomenumber and/or structure.
Macro-visualization of the DNA in
terms of chromosomes
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Is the visualization of changes, which
affect the normal structure and number ofchromosomes of an individual.
Visualization of evolution
MAIN PURPOSE
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1891 - 1956 (between 44 & 48)
1956 set as 2n = 46 (Tjio & Levan).
Setting the number of chromosomes
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In mammals, determined by chromosomecomposition
Humans: 46 chromosomes total 23 chromosome pairs, 22 pairs are autosomes 1 pair of sex chromosomes
Y chromosome carries genes for male developmentXX = femaleXY = male
How is the sex of the offspring determined?
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KARYOTYPING Karyotyping is the arrangement of chromosomes
according to their size.
Banding pattern
Centomeric position
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Why do we do karyotyping?Pre-natal Samples
Amniotic Fluid
Product of Conception
Pre-natal Diagnosis
Autosomal Anomalies
Trisomy 13
Trisomy 18
Trisomy 21
Post-natal Samples
Blood
Bone Marrow
Post-natal Diagnosis
Autosomal Anomalies Trisomy 13
Trisomy 18
Trisomy 21
Turners syndrome
Klinefelters syndrome Trisomy X
Double Y syndrome
Proliferated Syndrome
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CHROMOSOME STRUCTURE
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Human Karyotype
46,XY
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...and centromere position.
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HOW TO GET CHROMOSOMESA variety of tissue types can be used to obtain
chromosome preparations.
Blood Bone marrow
Amniotic fluid
Product of conception.
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Human Karyotype
Procedure:
blood sample centrifugation
isolation of lymphocytes (phytohemaglutinin)
incubation in 0.075M KCl (Hypotonic bath)
2 fixation (methanol/ethanol:acetic acid; 3:1) drop on frozen slide from 15 - 25 cm.
Stain (Giemsa 4%)
visualization of well spread samples.
Photo karyotyping.
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Banding G: G banding pattern. Staining with
Giemsa. Q: G banding pattern. staining with
quinacrin orange.
R: Reverse G banding pattern. Staining with
Giemsa). C: Centromere and telomere banding
pattern (constitutive heterochromatin).
Staining with Giemsa )
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Smear
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Human Karyotype
46,XY
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Chromosomes can be identified by their size
and banding pattern...
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Human Aneuploidy in Sex
Chromosomes
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Turner Syndrome Frequency = 1/2000
45, X apparently independent of the mother's age.
It seems to be the fathers chromosome that
is missing.
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XYY Individuals
~5% criminals with violentand antisocial behavior are XYY,
but only 0.1% of males in population XYY
XYY Syndrome
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XYY Syndrome
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THANX
THE
END