Syndrome is the result of a segmental
aneuploid deletion of a small portion of the long arm of
Chromosome 7 (2n=46, 7q11.23-). The fluorescence in situ
hybridation (FISH) image for the stardard karyotype
[above, right] with two complete chromosomes shows
binding of a control
probe for another locus on the 7q arm, along with
an experimental probe for the elastin gene locus, which is present in
region on each of two
medium-sized metacentric chromosomes. The Williams karyotype
(above, left) shows one standard chromosome, to which
both probes bind, and one segmental aneuploid chromosome in which
control probe binds, which indicates a segmental
deletion of q11.23.
According to the Williams Syndrome Association, children
with Williams Syndrome are characterized by “[S]mall upturned nose, long
philtrum (upper lip length), wide mouth, full lips,
small chin, and puffiness around the eyes. Blue and
green-eyed children with Williams syndrome can have a
prominent "starburst" or white lacy pattern on their
iris.” Medical conditions include narrowing of
the aorta (aortic stenosis) and/or pulmonary arteries,
hypercalcemia (elevated blood calcium levels), low
birth-weight and/or ‘failure to thrive’, dental
anomalies, renal anomalies, inguinal hernia, hyperacusis
(hearing sensitivity, ‘startle
response’), low muscle tone and joint laxity.
Williams syndrome have a very endearing personality.
They have a unique strength in their expressive
language skills, and are extremely polite. They are
typically unafraid of strangers and show a greater
interest in contact with adults than with their
peers.... Most people with Williams syndrome mild to
severe learning disabilities and cognitive challenges.
Young children with Williams syndrome often experience
developmental delays. Milestones such as
walking, talking and toilet training are often
achieved somewhat later than is considered normal.
Distractibility is a common problem in mid-childhood,
which can improve as the children get older... Older
children and adults with Williams syndrome often
demonstrate intellectual "strengths and weaknesses."
What is the purpose of the Control Probe? Suppose you are a genetic
counsellor and perform the FISH test on a newborn child. What is
your interpretation if (1) The karyotype shows binding
of both the control and elastin probes to only one
chromosome, or (2) the karyotype shows binding only of
the elastin probe, (a) to one chromosome only, or (b)
two both chromosomes, or (3) The karyotype does not show
binding of either the control or elastin probes.