What are the main diseases caused by errors of the number of sex chromosomes in the cells of an individual?
Diseases caused by the abnormal number of sex chromosomes are called sex aneuploidies.
The major sex aneuploidies are: 44 + XXX, or trisomy X (women whose cells have an additional X chromosome); 44 + XXY, or Klinefelter's syndrome (men whose cells have an extra X chromosome); 44 + XYY, or double Y syndrome (men whose cells have an additional Y chromosome); 44 + X, Turner's syndrome (women whose cells lack an X chromosome).