1. KEY CONCEPT During meiosis, diploid cells undergo two cell divisions and make 4 haploid cells.

2. Meiosis I and Meiosis II each have four phases, PMAT.
Prophase I
DNA coils to make chromosomes (DNA had been copied in S period); sister chromatids are formed
Nuclear membrane disappears
Spindle fibers form
Synapsis occurs: homologous chromosomes find their pairs
Tetrads form: chromosomes twist around each other (ends stick together)
Crossing over occurs: portions of DNA are exchanged
homologous chromosomes
sister
chromatids

3. Metaphase I
Tetrads line up on the equator
Anaphase I
Pairs of homologous chromosomes separate; each chromosome (sister chromatid) is pulled to an opposite pole.
Telophase I
Cytoplasm divides to form two daughter cells, each with half the number of chromosomes.

4. Meiosis I

5. Meiosis II
Prophase II
New spindle fibers form
Metaphase II
Sister chromatids line up on the equator
Anaphase II
Sister chromatids separate and chromosomes are pulled to opposite poles

6. Telophase II
Spindle fibers disappear
Nuclear membranes form
Chromosomes uncoil
Cells separate to form a total of 4 daughter cells, each with half the chromosomes of the original parent cell.

7. Meiosis II

8. Gametogenesis: Producing gametes
Different between females and males.
Sperm develops flagella.
Sperm contribute only DNA to an embryo.
one cell (the egg) gets most of the contents; the other cells form polar bodies which are later destroyed.
Eggs contribute DNA, cytoplasm, and organelles to an embryo.