Unformatted text preview: Meiosis
Meiosis I (= reductional division) Stages: Leptotene: chromosomes attach themselves by telomeres to the inner membrane of
nuclear envelope. Lateral (axial) elements (of synaptonemal complex) are formed. Zygotene: homologues pair at their telomeres and begin to synapse forming the
synaptonemal complexes. Pachytene: pairing (synapsis) is completed and crossing over is executed. Diplotene: homologous chromosomes are beginning to repulse each other, chiasmata
form. Diakinesis: bivalents move to the equator of the cell. Metaphase I: bivalents orient themselves on the equator. Chiasmata are on the equator
and homologous centromeres point at the opposite poles. Anaphase I: homologous chromosomes move to the opposite poles. Telophase I: a diad of daughter nuclei is formed. The nuclei have reduced chromosome
number (they are haploid). Interkinesis: resting stage between meiosis I and II. N 0 DNA replication occurs! Meiosis II (= equational division)
Prophase II: chromosomes condense.
Metaphase II: chromosomes orient themselves on the equator with their centromeres.
Anaphase II: Sister chromatids move to the opposite poles. Telophase II: Four haploid nuclei are formed. Ultimately, four cells (tetrad) develop. ...
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- Winter '08