Final answer:
Klinefelter's syndrome is a genetic disorder in males caused by an extra X chromosome, characterized by the XXY genotype.
Step-by-step explanation:
The correct answer regarding Klinefelter's syndrome is that it is a genetic disorder caused by the presence of an extra X chromosome in males. Therefore, the answer would be '1) It is a genetic disorder caused by the presence of an extra X chromosome in males.' This syndrome is characterized by the XXY genotype in males, which can lead to symptoms such as small testes, enlarged breasts, reduced body hair, and in some cases, sterility and reduced testosterone production. It is important to note that every X chromosome except one undergoes inactivation in individuals with Klinefelter syndrome to compensate for the excess genetic dosage, appearing as several Barr bodies in each cell nucleus.