1. Meiosis I Prophase I Condensation of the chromosomes
Homologous chromosomes pair up
Crossing-over takes place

2. Metaphase I, Anaphase I, Telophase I and Meiosis II
Homologous pairs line up in the middle of the cell
How one pair of homologous chromosomes lines up has no effect on how any other pair lines up.
Anaphase I
the chromosomes move to opposite sides of the cell.
Telophase I
Nuclear membrane appears.
Meiosis II
The 2nd division takes place producing haploid cells.

3. Normal Meiosis & Fertilization
Meiosis allows the number of copies of each kind of chromosome to be reduced by half. (1n)
Fertilization restores the chromosome count to the original number. (2n)

4. Crossing-over
The chromatids tangle allowing genetic material to be exchanged.

5. Nondisjunction