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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