1. Cell Division

2. A. Introduction
Multicellular & Unicellular organisms must divide to produce new cells for:
*Reproduction
*Growth (by increasing in cell #;
multicellular organisms only)
*Replace cells that have died from
disease, injury, old age

3. 2. Types of Cells
**Eukaryotic (multicellular) organisms have 2 types of cells=
Somatic Cells: Regular body cells that divide using Mitosis (used by unicellular
organisms to reproduce)
b. Germ Cells: Cells that produce gametes (reproductive cells known as the egg or sperm) and divide using Meiosis

4. 3. Cell Division & DNA
a. The nucleus of a cell contains a material known as chromatin which is actually DNA in a thin, spaghetti-like form. It tightly coils up to form chromosomes, but only during cell division.
centromere
Chromatid
Chromosome
Sister

5. Cell Division & DNA
b. During cell division, the chromatin condenses and coils into structures known as chromosomes.
c. Every organism of a specific species has the same number of chromosomes in each somatic cell.
EXAMPLES:.
*human = 46
*chimpanzee = 48
*chicken = 78
*fruit fly = 8

6. *Matching chromosomes form Homologous Pairs.
Cell Division and DNA
Chromosomes can be matched into pairs (one from mom and one from dad) by size and appearance.
*Matching chromosomes form Homologous Pairs.

7. Terms that refer to Chromosome Number:
e. Diploid: a cell that has a complete set of chromosomes. Both chromosomes in each homologous pair are present in the cell.
Example = a SOMATIC cell.

8. Terms that refer to Chromosome Number:
Haploid: a cell that has half of the complete set of chromosomes.
Only one chromosome of each homologous pair is present in the cell.
Example = GAMETES = Egg or Sperm

9. B. Cell Cycle G1 S G2

10. B. Cell Cycle *G1 = Growth 1: Cell is growing
Interphase: Cell is producing proteins and carrying out normal cell function.
NOT a phase of Mitosis or Meiosis!
*G1 = Growth 1: Cell is growing
*Synthesis: Cell is replicating DNA
*Growth 2: Cell is preparing to divide
2. Cell Division: Cell divides its genetic material in the nucleus by way of mitosis or meiosis.

11. Cell Cycle Cytokinesis = the division of the cytoplasm following cell
division; NOT a part of
mitosis or meiosis.

12. MITOSIS
Definition = the division of the nucleus and the chromosomes of a diploid somatic cell that results in the formation of 2 identical, diploid somatic cells.

13. C. MITOSIS Stages: 1. Prophase Nuclear membrane & nucleolus disappear
Centrioles move to opposite sides of the cells
Chromatin becomes chromosomes
Spindle fibers appear; will help to move chromosomes

14. PROPHASE
CENTRIOLES
SPINDLES
CHROMOSOME
DISAPPEARING NUCLEAR ENVELOPE

15. PROPHASE
PROPHASE CELL

16. METAPHASE

17. METAPHASE
METAPHASE CELL

18. MITOSIS Chromosomes line up individually in the center of cell
2. Metaphase
Chromosomes line up individually in the center of cell
Spindles fibers connect to each chromosome at the centromere.

19. ANAPHASE

20. ANAPHASE
ANAPHASE CELL

21. MITOSIS
3. Anaphase
Chromatids of each chromosomes are separated by the spindle fibers
Separated chromatids move to centrioles at opposite sides of the cell

22. TELOPHASE

23. TELOPHASE

24. MITOSIS 4. Telophase Chromosomes uncoil into chromatin
Nuclear membranes form around each area of chromatin
Spindle fibers disappear
Nucleoli reappear in each nuclear area
Two nuclei form, each with a complete set of chromosomes.
Mitosis ends (cells not separated yet)
A cleavage furrow begins to form

25. D. AFTER MITOSIS Cytokinesis
The division of the cytoplasm following mitosis or meiosis
In animal cells, a cleavage furrow divides the cytoplasm to form two new cells.
In plants, a cell plate divides the cytoplasm
Cells are genetically identical
Called Daughter Cells
Each is diploid
Each is in interphase

26. CYTOKINESIS

27. Mitosis and Cytokinesis Animation
Cell division animation
New Animation of mitosis
Actual mitosis