1. Mitosis Why do cells divide?
The larger the cell, the more demands are placed on its DNA
Trouble with a larger cell moving nutrients and wastes across the cell membrane
Cell Cycle: the sequence of growth (preparation) and division of a cell
Accurate cell division and regulation of the cell cycle is critical to the health of the cell
Mistake in cell cycle can lead to cancer (uncontrolled cell division)
Guarantees genetic continuity, growth, repair

2. Stages of Mitosis: Interphase
DNA doubles
Centrioles double
Chromosomes difficult to see (dots)
Nucleolus and nuclear membrane visible
“Resting Stage”

3. Prophase Longest Stage Chromosomes long and thin
Nucleolus and nuclear membrane disappear
Spindle forms
Centromere hooks doubled chromosomes to the spindle
Centrioles at both ends of the spindle

4. Metaphase Middle Stage Shortest Stage
Doubled chromosomes line up at equator

5. Anaphase
Chromosomes pull apart to opposite poles

6. Telophase Last Stage of Mitosis Animal Cell breaks apart
Plant Cell breaks apart
Result: 2 identical daughter cells

7. Meiosis Cell division of the sex cells
Spermatogenesis: meiosis of the sperm
1 Immature sperm cell results in 4 mature sperm
Oogenesis: meiosis of the egg
1 Immature egg cell results in 1 mature egg (3 egg cells die = yolk)
How does meiosis differ from mitosis?
Haploid chromosome # (N) transmitted to each cell
N sperm + N egg = 2N zygote (diploid chromosome #)
2 separate divisions (No 2nd Interphase)
Prophase I: Homologous chromosomes line up and chromotids “cross over” (Synapsis); leads to variety