1. 11.4
Meiosis

2. Chromosome number
Organisms have 2 copies of each chromosome (1 from each parent) = Homologous chromosomes

3. If a cell contains both sets of homologous chromosomes = diploid (2n)
Ex. Human diploid # is 46

4. If a cell contains one set of chromosomes (half the total) = haploid (n)
Ex. Human haploid # is 23

5. Meiosis
= nuclear division that reduces the number of chromosomes by half
- makes gametes ( ____ ) from diploid reproductive cells
Involves 2 divisions  4 haploid cells
Meiosis I & Meiosis II

6. Meiosis I - homologous chromosomes separate Prophase I
- prophase, plus, pairing of homologous chromosomes
- pairing = synapsis  forms a tetrad
- crossing over – when portions of chromatids break off and attach to adjacent chromatids in homologous chromosomes

8. Metaphase I
Anaphase I
- independent assortment – leads to greater genetic variation
Telophase I
Cytokinesis I

9. Result?
- 2 new cells with haploid number (one chromosome from each homologous pair)

11. Meiosis II - chromatids of each chromosome separate Prophase II
Metaphase II
Anaphase II
Telophase II
Cytokinesis II

12. Result?
- 4 new haploid cells
- in males  spermatogenesis (4 sperm cells)
- in females  oogenesis ( 1 egg cell, 3 polar bodies)