['To determine the effect of mutant mitochondria on preimplantation embryo development and of preimplantation embryo development on the survival of mutant mitochondrial DNA.', 'Laboratory research.', 'Academic research laboratory.', 'None.', 'Mutant and wild-type mitochondria, fractionated from tissue obtained from a patient with MELAS syndrome, a mitochondrial disease, were microinjected into mouse zygotes. Control zygotes received either no injection or sham injection.', 'Preimplantation embryo development and survival of mutant mitochondrial DNA as determined by polymerase chain reaction analysis.', 'After microinjection into zygotes, the MELAS mutation could be identified by polymerase chain reaction until the hatched blastocyst stage of embryo development. The survival of MELAS-injected zygotes, observed for 4 days after injection, did not differ from the survival of zygotes injected with wild-type mitochondria or from the survival of uninjected or sham-injected controls.'] Does microinjection of mitochondria into zygotes create a model for studying the inheritance of mitochondrial DNA during preimplantation development?