In order to test homogeneous yeast populations, pure spore cultures were obtained by using this strain whose sporulation efficiency is 100%. To prepare spores, cells were grown on YPD plates, replicated on SPOIV medium (2% potassium acetate, 0.25% yeast extract, 0,1% glucose). Zymolyase (2 mg/ml) was used to digest ascum and liberate spores. Zymoliase was inactivated by heat (65°C for 2 minutes) and washed away carefully together with the remainings of the empty ascus, by resuspending twice the spore culture in 500 µl of distilled water centrifuging and disc...