It is now possible in certain cases to to insert absent genes into humans. This is being used experimentally as treatment for certain deficiency diseases. It is already being considered that there could be genetic interventions capable of enhancing growth, mood or intelligence, or reducing susceptibility to a disease.
About 40 baby girls have been born in Japan by a technique of chromosome manipulation. There it is girls are the sex of choice because of certain types of hereditary conditions peculiar to men, such as haemophilia and colour blindness.