Gene therapy as practiced at PL 5-targeting specific cells for localized modification-affects only the patient directly receiving the treatment. She is unable to pass the modifications on to her offspring. However, once the technology reaches the point in PL 6 that it can imbue the subject with new special qualities, the subject has been changed at a basic genetic level and the traits may be passed along to children.
This process has the potential to create an entirely new race- winged humans, for example. And if the genetic manipulation is extensive enough that the subject's DNA is no longer compatible with naturally occurring DNA-if she can no longer mate with normal m embers her own kind-the subject has actually been transformed into a new species. Such manipulation generally is not possible until PL 7.
The most common use for such extensive genetic manipulation is to create humans or other creatures who are capable of surviving in conditions that would normally be deadly.