Meiosis Phases

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Meiosis Phases

  1. 1. Meiosis IMeiosis I • Prophase I – homologous chromosomes form tetrads & crossing over occurs • Metaphase I – tetrads line up along the middle • Anaphase I – homologous chromosomes separate • Telophase I – two nuclei form • Cytokinesis I – cells separate 2N N N
  2. 2. Meiosis IIMeiosis II • Prophase II – spindle forms, prepares for division • DNA replication DOES NOT occur between Meiosis I & II • Metaphase II – chromosomes align along the center • Anaphase II – sister chromatids separate • Telophase II – nuclei reform; cytokinesis N N N N NN Looks A LOT like MITOSIS!
  3. 3. Meiosis SummaryMeiosis Summary  Chromosome number is cut in half!Chromosome number is cut in half!  Produces haploid gamete cells – egg and spermProduces haploid gamete cells – egg and sperm  Tetrads form during Prophase ITetrads form during Prophase I  Crossing over occurs in tetrad formation – leadsCrossing over occurs in tetrad formation – leads to increased genetic variationto increased genetic variation  Two cell divisions, but DNA does not replicateTwo cell divisions, but DNA does not replicate between divisionsbetween divisions  Results in 4 sperm cells in men and 1 egg in womenResults in 4 sperm cells in men and 1 egg in women  Which chromosomes wind up in which sex cells?Which chromosomes wind up in which sex cells? It’s random…due to independent assortment!!It’s random…due to independent assortment!!

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