Genetic modifications

Having read a fair amount of Science Fiction over the course of my life, I was intrigued to see a piece in today's NYT decrying the possibility of modifying the eggs of women predisposed to pass on genetic diseases to their offspring.  Instead of using another woman's egg and in-vitro fertilization, scientists would pluck the offending genetic material from the donee's egg and use the healthy egg as a host by expunging the genes which make up the essential humanity of the other.  While I applauded this sort of thing in a sci-fi novel, I can't help but wonder if we are careening down a blind alley if this is pursued on a real life basis.  The horrors which usually ensue in the novel are blithely waved off by today's intrepid doctor's.  This is only going to help women who would otherwise pass on deadly genes to their children.  Unfortunately, that is also how many of the sci-fi novels also start.  Soon after, the temptation to further meddle with the culmination of a billion years of evolution becomes too great and the "fun" begins.