- jonb,
The male "gene" is SRY, or sex-determining region of the Y chromosome. XYY males are actually fairly normal, but tend to have a lower sperm count. XYY males average about 7 cm taller, and more prone to acne, but genital growth and secondary sex characteristics are normal. They also tend to be early bloomers.
And for the record, there is no proven correlation between XYY and mental retardation, narcissistic personality disorder, or antisocial personality disorder.
And for the record, there is no proven correlation between XYY and mental retardation, narcissistic personality disorder, or antisocial personality disorder.