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Name: Annie
Status: Student
Grade:  6-8
Location: CA
Country: United States
Date: January 2005

Is it possible to survive with only one chromosome 21? If so, what would that condition be called?

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


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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