The scope of inheritable genetic modification

Inheritable genetic modification (IGM) can be defined as the modification of the inheritable genetic information of an animal or person so that the alteration or added trait(s) corresponding to the transferred gene(s) are passed on to descendants. However, IGM has also been used to describe early intervention in the developing embryo that results in large-scale modification of the cells of the eventual person or animal that is not aimed at being inheritably transmitted. This methodology has been proposed to treat genetic diseases that result in perinatal death, so-called in utero gene therapy. Although the two procedures are quite different in their goals, they overlap both in terms of their technology and in the heightened possibility that somatic embryo modification might lead to an inadvertent germ-line change compared to other types of somatic cell gene transfer (SCGT). This is simply due to the small size of the embryo and the rapid turnover of cells, circumstances that favor transduction of a large number of cells in the embryo, but also make it seem more likely that inadvertent germ-line alterations will be made. Indeed any gene when delivered to the systemic circulation may cause the unintended consequence of the modification of germ cells. The consequences presumably would be unintentional because in most jurisdictions including the U.S.A., the U.K., and Australia, any intentional modification of the germ line is, for practical purposes, forbidden.