Abstract: | Cells of Paramecium tetraurelia, stock hrd, cultured in a micro-capillary containing 1 μl fresh culture medium, expressed mating activity through the whole cell cycle. Mating-reactive G2 phase cells can conjugate with cells of other phases. The G2 phase cells, which have double (4C) the normal micronuclear DNA content, undergo pre-meiotic DNA synthesis when conjugated with G1 phase cells. The micronucleus of the progeny from the cross between a G1 and a G2 cell becomes triploid. |