1. Cell Division

2. To replace old/damaged cells
Cells divide…
To replace old/damaged cells Or
To reproduce

3. Prokaryotic cell division
Called binary fission (form of asexual reproduction)
Only 3 stages
a) DNA replicates
b) cell growth
c) new cell wall forms & divides the cell
**remember prokaryotes are single celled bacteria & they don’t have a nucleus!!!!!!!

5. Eukaryotic cell division
Eukaryotes have a cell cycle.
Eukaryotes have 2 different types of cell division.
1) mitosis – forms 2 diploid cells identical to the parent cell
2) meiosis – forms 4 haploid gametes that are genetically different from the parent cell

6. THE CELL CYCLE Interphase – growth stage * longest phase
* has 3 phases
1) G1 = cell growth
2) S = DNA replication
3) G2 = new organelles, prep for division

8. 2) Mitosis (M phase)- division of the nucleus
* the nucleus & DNA divided
* 4 phases of mitosis
1) prophase
2) metaphase
3) anaphase
4) telophase

11. Mitosis

12. 3) Cytokinesis – the cell divides into 2 cells and each will start on their cell cycle
* different for plant & animal cells

13. Cell cycle

14. Meiosis Used in spermatogenesis & oogenesis.
2) Forms the gametes needed for sexual reproduction
3) The gametes will be haploid (have ½ the number of chromosomes)

15. 2 main stages of meiosis Meiosis I * has 4 phases (P, M, A, T)
* the parent cell produces 2 diploid cells (similar to mitosis)
* Major difference = crossing over in prophase I produces new combination of genes!!

16. Crossing over

22. Meiosis II
* has 4 phases
(same as mitosis & meiosis I)
* Major difference – during anaphase II –the sister chromatids split
* end up with 4 haploid genetically different gamete cells (sperm or egg)

23. Meiosis

24. Asexual vs. Sexual reprod.
No exchange of
genetic information.
The offspring are genetically identical
to the parent cell.
No meiosis (no gametes!)
2 parents exchange genetic information.
Offspring has a combination of genes from both parents.
Sperm fertilizes egg (gametes produced during meiosis)