karyotyping lab
TRANSCRIPT
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Chromosomes and Karyotyping
Dr. Nisrine Bissar-Tadmouri
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Chromosomes
Karyotype:display of
chromosomes
paired according
to their size,location of the
centromere, and
staining patterns.
organized into 7groups
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Cytogenetics
a discipline that matches phenotypes with detectable
chromosomal abnormalities.
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Malekaryotype
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Trisomy 21or
Downs
Syndrome
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Submetacentric
Metacentric
Acrocentric
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Diagnosis of chromosome abnormalities
Child born
take blood and look at lymphocytes
Unborn child
Prenatal DiagnosisChorionic villus sampling (CVS)
Amniocentesis (AF)
Fetal Blood Sampling (FBS)1) Karyotype
2) FISH: Fluorescent in situ Hybridization
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Indications for Karyotyping
An individual with characteristics of one of thecommon chromosomal syndromes (Downs,
Turners, kleinfelter etc..)
The presence of multiple congenital anomalies(usually associated with mental retardation)
A couple with multiple miscarriages
An individual at risk for inheriting ortransmitting a chromosomal rearrangement
(translocation)
A child with ambiguous external genitalia
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http://upload.wikimedia.org/wikipedia/commons/5/57/FISH_%28Fluorescent_In_Situ_Hybridization%29.jpg -
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Downs syndrome
FISH is used for fine
details like
submicroscopic
deletions, or even genelevel mutations
(hard to detect on the
Karyotype)
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Screening
Both in first and second trimester
Maternal serum screening
Ultrasound
Indicates which should go forward for invasive
procedure
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Human Karyotype preparation for prenatal diagnosis
10-12 weeksAround 16
weeks
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How to prepare a chromosome spread
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sample
0.7 ml heparinized blood
10ml cell growth medium containing
phytohemagglutinin (mitogen)
Incubate 72 hrs at 370C
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synchronization
100 ml colcemid
Incubate for 20 min at 370C
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Cell collection
Centrifuge at 1200 rpm for 10 min
Remove medium leaving 0.5 ml
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swelling
Resuspend cells in the remaining medium
Add 2 ml of 0.075M KCl drop by drop
Add 8 ml of the KCl solution
Incubate for 15 min at 370C
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fixation
Centrifuge and remove supernatant
Resuspend cells and add 10 ml freshly prepared fixative
(methanol: glacial acetic acid, 3:1) for 10-15 min
Centrifuge and remove supernatant
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Metaphase spread
Resuspend in small amount of fixative
Drop suspension on microscop slide
Stain by immersing in Giemsa stain 7-10 min
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Writing karyotype information
Abbreviation What it means
46, XY Normal male
46, XX Normal female
45, X Turner syndrome female
47, XXY Klinefelter syndrome male
47, XYY Jacobs syndrome male
46, XY del (7q) Male missing part of long arm of chromosome 7
47, XX+21 Female with trisomy 21
46, XY t (7;9)
(p21.1;q34.1)
Male with translocation between short arm of
chromosome 7 band 21.1 and long arm of chromosome
9 band 34.1
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Writing karyotype information
Abbreviation What it means
46, XX, del(5)(p15.3) Cri du Chat syndrome female
46, XY, dup(21)(q21) Male with duplication of band q21 on chr 21
45, XX, inv(9)(p12q13) Female with percentric inversion on chr 9
46, XX,del(15)q12 Female with Prader-Willi
46, XX/45,X0 A mosaic case of Turner Syndrome