Figure 2.

Biased inheritance of an ADE2 gene drive element is readily visible in S. cerevisiae. (A) Mutations in ADE2 generate a red phenotype on adenine-limiting media due to the buildup of red pigments. Mating a red mutant haploid to a wild-type haploid produces cream-colored diploids, which yield 50% red and 50% cream-colored progeny upon sporulation. (B) When haploids with a gene drive element targeting ADE2 mate with wild-type haploids in the presence of Cas9, cutting and subsequent replacement or disruption of ADE2 produces red diploids that upon meiosis yield exclusively red progeny. (C) Diploids produced by mating wild-type and ade2::sgRNA gene drive haploids yield cream-colored colonies in the absence of Cas9 or when the target site is removed by recoding but uniformly red colonies when both are present, demonstrating Cas9-dependent disruption of the wild-type ADE2 copy. (D) Spores from 15 dissected tetrads produce uniformly red colonies on adenine-limited plates, confirming disruption of the ADE2 gene inherited from the wild-type parent. In the absence of the target site or Cas9, normal 2:2 segregation is observed.