1. CELL DIVISION
mitosis & meiosis

2. Forms of DNA
When the cell is NOT dividing = chromatin
When the cell IS dividing = chromosome
Monovalent
chromosome
Bivalent
chromosome

3. Why do cells divide?
Replacement - cells wear out & die
Repair - tissues can be damaged by injury or infection
Growth of the organism
Reproduction

4. Types of cell division
Mitosis
New cells are identical to the old cells
Chromosome number is the same in parent & daughter cells (diploid -2n)
Growth, repair, & asexual reproduction

5. MITOSIS

6. Meiosis
Parent cell divides twice to produce 4 cells
Produces gametes (sex cells –sperm/eggs)
Daughter cells have half the original number of chromosomes (haploid -1n)

7. 4.When two gametes join to form a zygote, it will have the normal # of chromosomes

9. MEIOSIS

10. 5. Daughter cells are not Genetically identical
a.) Homologous chromosomes separate, sending one version of each to the new cells.
b.) Crossing –Over: sometimes chromosomal segements are exchanged between Homologous Chromosomes.

12. Phases of Mitosis
Interphase
Growth & normal cell activities
DNA = chromatin
*as the cell prepares for division, DNA is duplicated

13. Prophase
Chromatin thickens & reveals duplicated chromosomes (bivalent)
Centrioles move to poles
Nuclear membrane dissolves

14. Metaphase
Bivalent chromosomes line up along equator of cell
Chromosomes attach to spindle fibers

15. Anaphase
Spindle fibers pull monovalent chromosomes to opposite ends of cell
**an identical set of chromosomes moves to each pole

16. Telophase
Chromosomes uncoil & become chromatin again – Nuc. Memb Reforms
Cytokinesis: cell membrane pinches in to form 2 separate cells

17. Phases of Meiosis
Cells go through two rounds of division during meiosis, resulting in 4 haploid cells

18. Meiosis I & II
Section 11-4
Diff. genes
Same genes