Biomedical Engineering Reference
In-Depth Information
Table 7.2 Other contiguous gene disorders, their chromosome locations and
phenotypic effects
Syndrome
Chromosome
location
Symptoms
Langer-Giedion
del(8q24.1)
Mental retardation in most cases,
multiple catrtilaginous exostoses,
sparse scalp hair, bulbous or
pear-shaped nose, cone-shaped
phalangela epiphyses
WAGR
del(11p13)
Wilms kidney tumor, Anirida,
Genito-urinary dysplasia and mental
retardation.
Beckwith-
Wiedemann
dup(11p15.5)
Macroglossia, exomphalos,
visceromegly, giantism and a
predisposition to malignancy.
Prader-Willi
del(15q11-q13)
(pat)
Mental retardation, obesity,
hypotonia, dysmorphic features and
hypopigmentatyon.
Angelman
del(15q11-q13)
(mat)
Mental retardation, seizures,
ataxic gate, hand fl apping and
inappropriate laughter.
Rubinstein-Taby
del(16p13.3)
Mental retardation, broad thumbs and
toes, and dysmorphic features.
Smith-Magenis
del(17p11.2)
Hyperactive and self-destructive
behavior, mental retardation and
dysmorphic features.
Miller-Dieker
del(17p13.3)
Lisencephally, mental retardation and
early childhood death.
Di George/
Velo-
Cardio-Facial
del(22q11.2)
Absent or hypoplastic thymus and
parathyroid, cardiac malformations,
dimorphic features, mental
retardation and cleft palate.
￿ ￿ ￿ ￿ ￿ ￿
are collectively called contiguous gene syndromes. In most of these exam-
ples, molecular cytogenetic methods are needed to demonstrate these dele-
tions. While the loss of genetic material on the light microscope level is very
small, these deletions represent the loss of a signifi cant number of base pairs
and often result in the deletion of several genes that are closely linked to
each other. The term contiguous gene disorder refl ects the loss of more than
one closely-linked gene resulting in the observed phenotype.
One good example of these diseases is Williams Syndrome, del(7q11).
This disorder is characterized by mental defi ciency, unusual faces, gregarious
personalities, heart anomalies and idiopathic infantile hypercalcemia. The
disease is usually sporadic and one often sees supravalvular aortic steno-
sis (SVAS) in Williams patients. Interestingly, SVAS is autosomal dominant
and the fi nding of the deletion at 7q11 in Williams syndrome also localized
Search WWH ::




Custom Search