Fig. 2

Illustration of one-cell embryo injection for CRISPR-Cas modification of a mammalian embryo. The nuclease components (the nuclease Cas9, and the short guide RNA (sgRNA)) are injected into a fertilized egg that has two nuclei derived from the male and female parents. The targeted modification (indicated by ‘x’) can occur in one or both nuclei, and the zygote proceeds to divide and form subsequent embryo stages