The karyotype in Klinefelter's syndrome is

1. Klinefelter's syndrome is caused by an additional copy of the X chromosome. 2. Adding one chromosome to the normal 46 gives 47 in total. 3. The sex chromosome complement becomes XXY, so the karyotype is 47, XXY. 4. Such an individual has overall masculine development with some feminine characters. 5. 45, XO is the karyotype of Turner's syndrome instead. _Source: syllabus Biology Ch4 'Principles of Inheritance and Variation'_