1. Cell Division
Continuity of Life

2. Common Features of all types of cell division
DNA replication must occur prior to cell division
DNA must be distributed to daughter cells
Daughter cells contain equivalent quantities of DNA

3. Types of cell division Binary fission Mitosis Meiosis
Occurs in Prokaryotic organisms
Purpose- growth in numbers
Mitosis
Occurs in most eukaryotic cells
Maintains chromosome number
Meiosis
Occurs in germ cells
Purpose- produce haploid cells

4. Binary Fission Simple process Single chromosome Duplication of DNA
Invagination of plasma membrane
Formation of daughter cells
Time frame- 15 minutes to several hours
Video

5. Mitosis Form of nuclear division Complex process
Several linear chromosomes involved
Chromosome number maintained
4 major steps required
Steps result in appropriate distribution of chromosomes
Mechanism of growth for most eukaryotic cells
Carried out in somatic cells

6. Steps in Mitosis Interphase Prophase Metaphase Anaphase Telophase
(Cytokinesis)

7. Prophase Chromosomes condense
Centrosome (may contain centriole) duplicates
Nuclear envelope breaks up
Spindle fiber forms from microtubules
Chromosomes hooked onto spindle fibers

8. Chromosome Structure

9. Condensed DNA

10. Metaphase Spindle fibers pull chromatids in opposite directions
Chromosomes align at the cell equator
Concludes when chromatids separate

11. Anaphase Chromatids now unduplicated chromosomes
Chromosomes move to opposite poles of the cell
Concludes when chromosomes reach opposite poles

12. Telophase Chromosomes decondense Nuclear envelope reforms
Cytokinesis usually begins

13. Cytokinesis Cytoplasmic division
Animal cells form furrow by contracting microfilaments at the equator
See text page 133
Plant cells form a cell plate by depositing vesicles containing cellulose at the equator
video

14. Cell cycle Interphase G1- Cell growth S- DNA replication
G2- Preparation for mitosis
M- Mitosis
G0- waiting mode
video

15. Meiosis Form of nuclear division Reduces the chromosome number by ½
Two stages
Meiosis I
Meiosis II
Crossing over between homologues
Occurrs in all sexually reproducing organisms
Produces gametes in most organisms
Haploid cells
Provides genetic diversity
Stages similar to mitosis

16. Cancer
Loss of cell growth control
No G0
Check points transgressed