Fig. 1: The tGD system allows simultaneous super-Mendelian inheritance of two transgenes.
a Schematic of the tGD genetic arrangement with two elements that can be kept separated as different transgenic lines. The Cas9 transgene is inserted in the genomic location targeted by the gRNA-A, while a separate cassette expressing a tandem-gRNA construct (gRNA-A, gRNA-B) is inserted at the location targeted by gRNA-B. Upon genetic cross, each of the gRNA-A and gRNA-B combines with Cas9 to generate a double-strand DNA break at each locus on the wild-type allele (dotted purple and brown arrows, respectively). Each break is then repaired by the homology-directed repair (HDR) pathway using the intact chromosome carrying the transgene as a template. b Outline of the genetic cross used to demonstrate tGD in fruit flies, indicating transgenes and wild-type allele location on different chromosomes. Sex of the individuals is indicated with symbols “♂” for males and “♀” for females. F0 males carrying a DsRed-marked Cas9 transgene inserted into the yellow locus were crossed to females carrying a GFP-marked cassette containing two gRNAs (y1–e1) inserted into the ebony coding sequence. Transheterozygous F1 females (carrying both Cas9 and gRNAs) were crossed to wild-type males to assess germline transmission rates of the fluorophores marking the transgenes in the F2 progeny. The conversion events are indicated by the red and green triangles in the F1 females. c Single F1 female germline inheritance output is measured as GFP and DsRed marker presence in the F2 progeny. The black bar represents the inheritance average. The blue shading represents the deviation from the expected 50% “Mendelian” inheritance. Inheritance average, standard deviation, number of samples (n), and total number of flies scored in each experiment are represented over the graph in line with the respective data. Raw phenotypical scoring is provided as “Supplementary Data 1”.
