Current applicable assisted reproductive technologies for mitochondrial replacement. From an MII oocyte with mutated mtDNA, spindle or PB1 is isolated and transferred to an enucleated MII oocyte with healthy mtDNA. Reconstructed oocytes by ST or PB1T are fertilized with sperm. In the zygote with mutated mtDNA, PNs or PB2 can be transferred to enucleated zygotes with healthy mtDNA. Two PNs are enucleated for PNT while only one PN is for PB2T. For SCNT, the fibroblasts carrying mutant mtDNA are transferred to enucleated MII oocytes with healthy mtDNA. Reconstructed SCNT oocytes are activated artificially. Embryos with healthy mtDNA can develop into ESCs or offspring. MII, metaphase II; mtDNA, mitochondrial DNA; ST, spindle transfer; PB1T, 1st polar body transfer; PB2T, 2nd polar body transfer; PNT, pronucleus transfer; SCNT, somatic cell nuclear transfer; ESCs, embryonic stem cells.