Gene therapy for individuals is mainly directed to somatic or germ cells. The present technology aims to insert a DNA segment in the recipient cells. This therapy is useful in Mendelian recessive diseases. There is an ethical moratorium to perform insertion gene therapy in germ cells, because this procedure increases the human genome. Somatic cell gene therapy cures individuals but increases the gene frequency of genetic diseases in the population. This occurs because the descendants of the cured patient should carry his or her «ill» genes. We denote by «DNA gene surgery» the procedure that replaces «ill» nucleotide(s) by healthy one(s) conserving the genome size and the gene context of expression and regulation. Several procedures for gene surgery have been applied to cells and animals. Those based on DNA repair as Chimeric RNA/DNA, one stranded oligonucleotides and tristranded DNA. Those based on DNA recombination with oligo-DNA or one stranded DNA, and transposable DNA segments. Gene surgery can be applied to germ cell gene therapy without ethical contraindications. It can cure Mendelian dominant diseases and it can be applied to heterozygotes. It preserves the regulation and expression gene context. If a technical safe procedure is available, the entire mankind could be treated and cured of all the Mendelian diseases, in one generation. Susceptibilities for all diseases could also be treated. The moratorium for research on germ cell gene therapy by gene surgery should be interrupted. Safe gene surgery is a moral imperative for gene therapy of patients and their descendants, for the treatment of dominant genetic diseases and for heterozygous carriers of recessive disorders (Rev Méd Chile 2003; 131: 1208-14).