Preimplantation genetic diagnosis (PGD) has been used in association with ART to analyze the DNA from embryos at the cleavage or blastocyst stage to determine genetic abnormalities (8). Recent techniques isolate a few cells from the trophectoderm that will become placenta or amnion during embryo development. These isolated cells can be genetically sequenced for disease mutations, and embryos negative for these mutations can then be transplanted into the mother. Multiple rounds of IVF are frequently needed to obtain healthy embryos. ART increases the chance of delivering a healthy baby without heritable genetic disorders caused by known mutations or chromosomal abnormalities (9).
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ST was pioneered in the monkey and has demonstrated the efficiency and safety of MRT verified by normal growth in the live birth and low levels of mtDNA carryover (16). Based on an ST study in the monkey, human ST was performed using oocytes with different mtDNA haplotypes for mtDNA tracking (17). In ST embryos, embryonic development and ESC establishment rates were similar to control IVF. In ESCs derived from ST embryos, mtDNA carryover levels were undetectable, however, certain haplotype combinations were reverted to maternal mtDNA, meaning 100% carryover (18). The world's first ST baby was born in Mexico (19). The mother harbored the mtDNA 8993T> G mutation for Leigh syndrome, and ST was carried out in order to avoid the transmission of this disease to her child. 2ff7e9595c
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