Genetic therapy, person-regarding reasons and the determination of identity

It has been argued, for example by Ingmar Persson, that genetic therapy performed on a conceptus does not alter the identity of the person that develops from it, even if we are essentially persons. If this claim is true then there can be person-regarding reasons for performing genetic therapy on a conceptus. Here it is argued that such person-regarding reasons obtain only if we are not essentially persons but essentially animals. This conclusion requires the defeat of the origination theory, which says that personal identity is determined by the identity of the foetus from which one originates. It is argued that the origination theory is false in the special case relevant to performing genetic therapy on a conceptus for person-regarding reasons.