Deletion of Chromosome 22 Long Arm
DiGeorge Syndrome
Individuals with the DiGeorge syndrome often have cardiac defects, immune
system deficiencies and can be moderately retarded. The cause of the DiGeorge
syndrome is a defect in chromosome 22, where one of the bands in the long
arm has been deleted. The deletion can be suspected by looking at the karyotype
and can be confirmed by FISH. (Fluorescence In-Situ
Hybridization)
This image shows the karytype of an individual with the DiGeorge
syndrome. By looking carefully at the pair of 22's, you can see that there
is a light band missing in the chromosome to the right. It might be easier
to see the defect in the composite karyotype of chromosome 22 from the
same individual.
The chromosome on the right in each pair is shorter than the one on
the left. This is due to the deletion of a bright band in the long arm
of the chromosome to the right, near the centromere.
Fluorescence In-Situ Hybridization. This image shows a paint of chromosome
22. In addition to the two normal copies of 22, there is also a small extra
piece, a marker, derived from 22 material.
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More
information on deletions of the 22 chromosome
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Images
from UW Pathology Department Cytogenetics Gallery
This image shows a FISH, where the probe has been used to locate the defect
associated with the Digeorge syndrome.