Recombination intermediates hold the chromosomes in synapsis, and the synaptonemal complex (SC) is present. During MI, the cohesion dissolves in the chromosome arms, but remains around the centromeres. Thus, the homologs remain attached, but the recombined chromosome can have arms that separate from each other.

During the MII division, the homologs separate, much as in mitosis in vegetative cells. In MII, the remaining cohesin around the centromeres is degraded so that the chromosomes separate properly.

a. Leptonema
Chromosome begin to condense, Homology Search, Initial pairing of homologous chromosomes.

b. Zygonema
Pairing of the homologues. SC (proteinaceous tripartite "ladder") is formed. The paired structures are called bivalents.

c. Pachynema
Intiate point by point synapsis of homologous chromosomes Shortening and coiling of paired chromosomes occurs--bivalents thicken. Can distinguish sister chromatids. Bivalent = Tetrad. Crossing over occurs

d. Diplonema
Crossing over occurs at chiasmata (breaks). Crossing over can involve nonsister chromatids. Chromatids begin to separate.

e. Diakinesis
Further shortening of chromosomes and separation. Linkage to the spindle. Nuclear membrane and nucleolus disappear. Terminalization: the chiasmata move toward the ends of the tetrad
END OF PROPHASE I