Evolution of the surface abundances of ³He and ¹⁴N (in mass fraction) and of the carbon and oxygen isotopic ratios as a function of stellar luminosity for the 1.25 M_⊙ models computed without (left) and with rotation (initial rotation velocity of 110 km s^-1, right). Thermohaline instablity is accounted for in both cases. In the left panels the black and red lines correspond to C_t = 10³ and 10⁴ respectively, while in the right panels C_t = 10³. Predictions are shown from the zero age main sequence up to the RGB tip. In the rotating case the first dredge-up starts at lower luminosity and ends at log(L / L_⊙) ~ 1 with slightly stronger abundance modifications than in the standard case. Also, thermohaline mixing sets in slightly earlier on the RGB at log(L_c,th/L_⊙) ~ 1.9 when rotation is accounted for.