Meiosis is a highly specialized cell division in which several events occur in a precisely defined order. Please order the meiotic events listed below
1. loss of cohesins near centromeres
2. chromatid pairing
3. chromosome condensation
4. chromosome replication
5. degradation of cohesins bound to chromosome arms
6. formation of chiasmata (chiasmata = plural of chiasma)
7. homolog pairing
8. alignment of chromosomes at the metaphase plate
4, 2, 7, 6, 3, 8, 5, 1. Chromosome replication (4) occurs during meiotic S phase, and immediately after replication the resultant sister chromatids are paired tightly by cohesins (2). During meiotic G2, or prophase, the two homologous chromosomes pair (7) and undergo recombination to produce reciprocal exchanges of genetic material that are visible as chiasmata (6). Meiotic division I begins with chromosome condensation (3) and proceeds to metaphase, when chromosomes align at a central plate (8). Anaphase of meiotic division I is triggered by loss of the cohesin glue on the chromosome arms (5), which allows the homologs to be segregated. Anaphase of meiotic division II is triggered by degradation of cohesins near the centromere (1), which allows sister chromatids to be segregated.
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