Fig. 4. Model of tGD transgene behavior in males and females.

a–c Schematic representation of the different scenarios observed in our tGD experiments when both elements (Cas9 and gRNA transgenes) are inherited together. a When the tGD chromosome (labeled in red) comes from the dad (sperm) any Cas9 activity was detected from zygote to cellularized embryo. The high F₂ inheritance rates in these conditions suggest that Cas9 action (red and yellow bars) is restricted to the germline development phase for the white and yellow genes, allowing efficient conversion (red dots) in this stage. Since the conversion process would occur after three pole-cell formation, this would be consistent with the 1–4 resistant allele range (blue and orange dots) captured from F₁ germline females analyzed. b, c We detected different outputs for both yellow and white loci when the tGD chromosome was inherited from the mother. b Cas9 cut (red bar) seems to occur at the zygote stage for the white locus since we only observe one resistant allele per each F₁ germline female that was analyzed. Consistently, this early cleavage event leads to 50% inheritance of our transgene precluding any further conversion event. c Cleavage of the yellow locus by Cas9 (yellow bar) seems to be delayed based on the super-Mendelian inheritance observed in the scored F₂ flies from some F₁ germline females. In this case, the Cas9 activity and the conversion process could occur in the zygote or syncytial blastoderm stage, and before the pole-cell establishment. This is reinforced by the the observed range of 1–3 resistant alleles (blue and orange dots).