Tags: Disease.
XYY syndrome is a genetic condition in which a human male has an extra male (Y) chromosome giving a total of 47 chromosomes instead of the more usual 46. This produces a 47XYY karyotype which occurs in 1 in 1000 male births.Some medical geneticists question whether the term syndrome is appropriate for this condition because its clinical phenotype is normal and the vast majority (an estimated 97% in Britain) of 47XYY males do not know their karyotype.
