  A second problem has to do with genetic interference. Suppose someone carried the gene for Huntington's disease (HD) and wanted a child.  There would be a 50/50 chance her child would inherit the HD gene. If there were genetic intervention available to eliminate the  possibility of her child carrying the gene, should she undergo it? It seems obvious she should, at least until we draw on some metaphysical considerations about identity. Suppose the genetic intervention  involved waiting until after fertilization and then altering the  genome of the fetus. What would be the identity of the  post-intervention child? Further, if its identity would be different  from the child that would have been brought into existence,  would the genetic interference be immoral in virtue of  preventing that other child's existence? Relevant to the  debate here is Saul Kripke's thesis about origins, that one person  could not have been someone else (Kripke 1980), and this is a thesis  with which advocates of the Biological Criterion of personal identity would likely agree: what makes me the particular individual I am is  my biological structure and its origins, and any other combination of my parents' sperm and egg would have produced a different individual. The question here, though, is whether or not some other  changes, after the combination of sperm and egg, would be sufficient  to produce a different individual. And if so, does this bear on the  morality of doing so? (For further discussion of these issues, see  Elliot 1993, Persson 1995, Belshaw 2000, Glannon 2001, and DeGrazia 2005: 244–268.)