Meiosis
i. Diploid cell with a single pair of homologous chromosomes (purple and green lines). Stages ii-iv; meiotic prophase. ii. Chromosomes replicate to give pairs of sister-chromatids connected by cohesion. iii. Homologs pair and become synapsed along their lengths. Crossing-over occurs during this period and the resulting chiasma links the homologs and thereby facilitates stable bipolar attachment to the meiosis-I spindle (shown in iv). v. Cohesion between the chromosome arms is lost and homologs are pulled to opposite poles. vi. Maintenance of cohesion between centromeres allows bipolar attachment of sister-chromatids pairs to the meiosis-II spindle. vii. The remaining cohesion is lost and sister-chromatids are segregated. Grey arrows indicate directions of the pulling forces generated by microtubules. Dashed lines indicate the planes of cell division.