Fig. 4: Effects of lethal/sterile mosaicism on the Reckh gene-drive system.

a A female heterozygous for the drive can produce eggs carrying a copy of the drive (green circle, kh^Rec+) or eggs carrying an EJ-induced nonfunctional resistant allele (white circle, kh⁻). Both types of eggs carry maternally deposited cytoplasmic Cas9/gRNA complexes (light blue filling) that can act on the incoming WT paternal allele (black circle, kh⁺). b The soma of individuals inheriting a copy of the drive from their mothers is a mosaic of cells with varying proportions of genotypes kh^Rec+/kh⁻, kh^Rec+/kh⁺, and kh^Rec+/kh^Rec+. Reckh individuals emerging from such embryos have at least one functional copy of kh provided by the drive system (kh^Rec+), therefore have GFP⁺/black eyes and females are fit for reproduction. c The soma of individuals inheriting an EJ nonfunctional mutation from their drive mothers is a mosaic of cells with genotypes kh⁻/kh⁻ or kh⁻/kh⁺. The ability of females emerging from such embryos to survive and reproduce depends on the proportion of somatic cells with genotype kh⁻/kh⁻. These individuals may display mosaic or white-eye phenotype if mutations affect the cells forming the eyes. Diploid cells in (b) and (c) that become germline progenitors also may be affected by mosaicism, which can affect drive capabilities.