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Single Chromosome Survival
Name: Annie
Status: Student
Grade: 6-8
Location: CA
Country: United States
Date: January 2005
Question:
Is it possible to survive with only one chromosome
21? If so, what would that condition be called?
Replies:
The condition would be called unisomy 21 in contrast to Down's syndrome
which is referred to as trisomy 21. There are no known cases of this
condition implying that it is lethal. The only known example of unisomy in
humans is Turner's syndrome in which the affected female carries only one
X-chromosome (designated XO). Look up
Turner's syndrome in a genetics textbook or do a search on Google.
Ron Baker, Ph.D.
So many of the older genetics textbooks gave worst case scenarios with
scary, dysmorphic photos often not typical of the population of people with
disorders. With new genetics discoveries, chromosomal differences are being
found in women with much milder presentations, and the consequences are not
as dire as previously thought.
According to the website of the Turner Syndrome Society
(http://www.turner-syndrome-us.org/),
women with Turner syndrome have normal
intelligence but may have learning disabilities - not the same thing as
mental retardation:
"Intelligence - Turner Syndrome individuals are of normal intelligence with
the same variance as the general population. They do, however, often have
difficulty with spatial - temporal processing (imagining objects in relation
to each other), nonverbal memory and attention. This may cause problems with
math, sense of direction, manual dexterity, non-verbal learning and social
skills. New and better ways to compensate for these problems are being
researched. The most common characteristics of Turner syndrome include short
stature and lack of ovarian development. A number of other physical
features, such as webbed neck, arms that turn out slightly at the elbow, and
a low hairline in the back of the head are sometimes seen in Turner syndrome
patients. Individuals with Turner syndrome are also prone to cardiovascular
problems, kidney and thyroid problems, skeletal disorders such as scoliosis
(curvature of the spine) or dislocated hips, and hearing and ear
disturbances."
Sarina Kopinsky, MSc, CGC
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Update: June 2012
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