Triple x. Triple XXX Rootbeer Drive

The extra X chromosome usually results from random error when the parents' egg or sperm cell is forming.

When the extra chromosome is due to incorrect cell division in the embryo, a girl may have a mosaic form of triple X syndrome.

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It's called triple X because they have an extra X chromosome in most or all of their cells.

Sometimes only some of the body's cells contain the extra X chromosome, a form of triple X syndrome called mosaicism.

Before birth, the condition can be found through a chromosomal analysis.