Figure 1

The meiotic process in S. pombe. When starved of nitrogen sources, haploid cells of the h⁺ and h^- mating type are arrested in G1, and secrete the mating pheromone to the opposite mating type cells. Upon sensing the pheromone, the cell elongates toward the opposite mating type cell and the cells fuse with each other (conjugation), followed by fusion of the haploid nuclei. The fused diploid nucleus then elongates (known as the horsetail nucleus), and moves back and forth between the cell ends (meiotic prophase). Meiotic DNA replication occurs at the beginning of this period, yielding a nucleus with 4C DNA contents. After movement ceases, the horsetail nucleus becomes rounded at the center of the cell, and proceeds with the first and second meiotic divisions to create four 1C nuclei.