Figure 1.

Human embryo twinning procedure. A) A triploid human embryo at cleavage stage with 8 blastomeres was used as the blastomere donor embryo (twin A). B) Half of the blastomeres were biopsied through the created hole in the ZP. C) An empty ZP by source of the discarded oocytes. D) The biopsied blastomeres were inserted into the empty ZP, one by one, as the blastomere recipient embryo (twin B) E) At the end of the procedure, twinned 4-cell embryos were cultured in vitro to the blastocyst stage (magnification 20×).