a, Karyotype analysis following whole-genome sequencing of either single blastomeres, a clump of three cells from a cleavage stage embryo or a clump of 3–5 cells from trophectoderm biopsies. Multiple biopies were analysed from embryos C8, C12 and C16. Analysis was also performed on blastocysts that developed following microinjection of Cas9 protein. The type of chromosome gains and losses are indicated. b, Representative karyotype analysis by whole-genome sequencing of human blastocysts. A representative graph indicating aneuploidy in embryos following Cas9 protein and sgRNA2b–Cas9 ribonucleoprotein complex microinjection. c, Phase-contrast images of starting blastocysts and blastocysts that developed following microinjection of the sgRNA2b–Cas9 complex compared to Cas9 protein-injected controls. White arrows point to the presumptive inner cell mass and a black arrow to a representative zona pellucida.