This week the NY Times had an interesting opinion column on mitochondrial replacement, a procedure currently under review by the FDA. The idea is that there is a cohort of inheritable diseases based on defects in the mitochondrial genome. In the embryo the mitochondria are all derived from the fertilized egg so the defects are passed from the female partner. Thus the approach for potential parents where the woman has a mitochondrial defect would be for in vitro fertilization followed by transfer of the fertilized nucleus to an enucleated egg from a healthy donor. Thus the embryo would have three parents, the male and female who contribute the nuclear genome and the female who contributes the mitochondrial genome.