Grit is a variation of conscientiousness (and is highly genetic)

conscientiousness per se, effortful control, self-control, and grit). These four different measures were substantially correlated; the coefficients ranged from 0.74 (0.72–0.76) to 0.79 (0.76–0.80)

…attributable to additive genetic factors, to an extent ranging from 62 (58–65) to 64% (61–67%)