How do the karyotype of a person with triple x syndrome differ from a normal karyotype?

A person with Triple X syndrome (or Poly-X syndrome)is a woman; hence the fact that they have all "X" chromosomes, versus 1 "X" and 1 "Y" (XY), which would be a male. The difference is that during cell reproduction they manage to get an extra "X" chromosome, thus giving them 3 "X" chromosomes(XXX) in some, but not all, of their cells. A normal female karyotypewould only have 2 "X" chromosomes (XX).

Usually, there are no visual symptoms and the disease cannot be recognized just by looking at the person. A woman with Triple X tends to be tall and thin. Most are not mentally retarted (though in rare cases, they can be), butmost usuallyhave reproductive and mentrual difficulties/problems.

More info at: http://en.wikipedia.org/wiki/Triple_X_syndrome

Hope this helps! ;)