XXX syndrome
A chromosome condition present in 1 in 1000 females, due to the presence of three X chromosomes rather than the usual two. The condition is associated with increased height but no malformations. Intelligence ranges from above normal to mild retardation. The average IQ is 85 to 90. Learning problems may be helped by early special education. Also known as triple X; triplo-X.
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- XXXX syndrome
A chromosome disorder in females caused by the presence of four X chromosomes rather than the usual two. The disorder is characterized by decreased intelligence (IQ 30 to 80; average 55), speech and behavioral problems, tall stature and reduced fertility. Also known as tetra-X syndrome.
- XXXXX syndrome
A chromosome disorder in females, caused by the presence of five X chromosomes rather than the usual two. It is characterized by decreased intelligence (IQ 20 to 75) and multiple malformations including upward-slanting palpebral fissures (eyeslits), heart defect, and small hands with incurving fifth fingers. It is the most severe extra-X syndrome in females. Also […]
- XY
The most frequent sex chromosome complement in human males.
- Xylitol
A sweetener that is found in plants and used as a substitute for sugar. Xylitol is called a nutritive sweetener because it provides calories, just like sugar. However, it is less likely than sugar to contribute to dental caries.
- XYY syndrome
A chromosomal disorder that affects males only, caused by the presence of an extra Y chromosome. Symptoms may include increased height, speech delays, learning disabilities, mild to moderate mental retardation, and behavioral disturbance. Also known as polysomy Y syndrome.