which of the following is caused by a gene on the x chromosome?
Klinefelter syndrome: 1  Klinefelter syndrome is caused by the presence of one or more extra copies of the X chromosome in a male's cells. 2  Males with Klinefelter syndrome typically have one extra copy of the X chromosome in each cell, for a total of two X chromosomes and one Y chromosome (47,XXY).
Some cells have the usual two sex chromosomes (either two X chromosomes or one X chromosome and one Y chromosome), and other cells have only one copy of the X chromosome. Women with Turner syndrome caused by X chromosome mosaicism (45,X/46,XX or 45,X/46,XY) are said to have mosaic Turner syndrome.