This set of links will take you through
an introduction to cytogenetic analysis. It is suggested that you
review meiosis and mitosis before proceeding. It will also help if
you have an understanding of some basic chromosome abnormalities (aneuploidies,
translocations etc.) You may work your way through the introduction
or you may go straight to trying your hand at completing normal or abnormal
karyotypes.
Introduction
Normal Karyotypes
Try your hand with normal karyotyping
by completing one or both of these partial karyotypes. Line up homologous
chromosomes by clicking on those chromosomes at the bottom of the window
and dragging them to their proper position. A proper match will be
acknowledged while mismatch will not. Remember, that in mammals,
the female is the homogametic sex (XX) and the male is the heterogametic
sex (XY). Determine the sex of each of these individuals.
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This phenotypically normal patient was referred because of
a nephew with downs syndrome shown to be the result of a robersonian translocation,
46, XY, -14, +t(14;21). The sister of the patient was shown
to be a balanced carrier of this translocation; 45, XX, -14, -21, +t(14;21)
[Full
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This 25 year old phenotypically normal patient has a severely
dismorphic son who, upon karyotypic analysis, was shown to have a partial
trisomy of chromosome 6 resulting from a translocation; 46, XY, t(3p;6p).
The patient was referred to rule out being a carrier for a balanced translocation.
[Full
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Abnormal Karyotypes
The following patients
were referred for cytogenetic analysis based on their clinical symptoms
or phenotypes. Complete one or more of these partial karyotypes then make
a diagnosis of the chromosomal abnormality.
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A 27 year old male of tall stature was
referred for mild mental retardation to rule out Fragile X syndrome [Full
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A blood sample was from a newborn with
multiple congenital anomalies including hypertlorism, cleft lip and palate,
polydactyly, and clenched fists. [Full
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This blood sample was taken from a one
day old infant girl with severe congenital anomalies including rocker bottom
feet, receding jaw, malformed and low set ears, and short sternum. [Full
Size] [Smaller]
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A blood sample taken from a 16 year old
man with mental retardation, macro orchidsm, large ears and hypermobile
joints. [Full
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An amniotic fluid sample was received
from a 32 year old woman who was 27 weeks pregnant. An ultrasound had found
her fetus to have a sloped forehead, a splayed spine, a small jaw and cystic
kidneys. [Full
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