Embryos are gonadally identical, regardless of genetic sex, until a certain point in development when the testis-determining factor causes male sex organs to develop. Therefore, SRY plays an important role in sex determination. A typical male karyotype is XY. Individuals who inherit a normal Y chromosome and multiple X chromosomes are generally male (such as in Klinefelter Syndrome , which has an XXY karyotype). Atypical genetic recombination during crossover when a sperm cell is developing can result in karyotypes that do not match their phenotypic expression.