Modelling

We use a discrete generation deterministic model to explore how the dynamics of gene-frequencies depend on underlying parameters. We suppose there are four possible alleles: Wildtype (W), driver allele (H), and two mutant alleles that are resistant to homing, R1 which is fully functional and R2 which is recessive but non-functional (i.e., H/R2 and R2/R2 type females are sterile). We assume alleles segregate at meiosis according to Mendelian inheritance except in W/H males and females, where segregation may be distorted by cleavage followed by either homing or non-homologous repair. Our model also allows for the possibility that eggs from females with at least one H allele will contain the driver nuclease (regardless of the egg’s own genotype), in which case cleavage and repair may occur in the embryo. The mathematical details of the model are given in the S1 Text, and model outputs from user-defined parameters values can be seen using a computable document format (Wolfram CDF Player) available as a file(S1 File). Baseline parameter values for the model are provided in the legend accompanying Fig 4.