Triple-X syndrome

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Definition

noun

A genetic condition in which a female has an extra X chromosome


Supplement

In humans, the sex chromosomes are the X chromosome and the Y chromosome. The basis of sex determination in humans is on the pair of sex chromosomes present in an individual. For instance, females have a pair of two X chromosomes whereas males have one X chromosome and one Y chromosome. There are instances though when certain individuals have a different set of sex chromosomes. An example is the so-called triple X syndrome, which is characterized by having an extra X chromosome.

Triple-X syndrome is a genetic condition in certain females wherein there is an extra X chromosome in each of the cell. Microscopic observation of the cell reveals twin Barr bodies rather than the normal XX complement. Karyotyping results in a total of 47 chromosomes due to the presence of an additional X chromosome apart from the other two X chromosomes. Thus, it is also called trisomy X. There are instances though wherein only some of the cells have an extra X chromosome; they are referred to as 46,XX/47,XXX mosaics.

The common physical features of females with triple-X syndrome are having a tall stature, epicanthic folds, and poor muscle tone. Other symptoms include learning disabilities, speech and behavioral problems, seizures, and kidney problems.


Also called:

  • 47,XXX syndrome
  • triplo-X syndrome
  • trisomy X
  • XXX syndrome

See also: