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. 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. 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!!