1. Cell Division
Making New Cells

2. Cell Division Cells come from pre-existing cells…
Cells need to reproduce!
Single-celled organisms -- asexual reproduction.
Multi-celled organisms – growth.
Cell Division = Cytokinesis
Nuclear Division =
Karyokinesis

3. Prokaryotes – Binary Fission
Simple

4. Eukaryotes – more complex
Chromosomes
Chromosome Structure
Chromatin
Unduplicated
Duplicated
Chromosome Number
Diploid
Somatic cells (body cells)
Haploid
Germ cells (sex cells)

5. Karyokinesis Mitosis Meiosis Somatic cells (body cells)
“Cloning” of genetic information – exact copies made and distributed to new cells.
Chromosome # is retained (stays the same).
Meiosis
Germ cells (sex cells)
Genetic information is shuffled – new cells are each different.
Chromosome # is cut in half.

6. Cell Cycle

7. Chromosome Duplication
During S-phase = “Synthesis”
Why?....
So that later, the sister chromatids can separate into different (new) cells!

8. Mitosis
Prophase
Metaphase
Anaphase
Telophase

9. Prophase Nuclear Envelope Disappears Nucleolus Disappears
Chromosomes Condense
Chromatin Chromosomes
Spindle Fibers (Microtubules)
Attach to Centromeres
Attach to M.T.O.C.s

10. Metaphase Chromosomes line up on the ‘Metaphase Plate’
pushed & pulled by the spindle fibers
Spindle Apparatus well developed.

11. Anaphase Chromosomes each broken at their centromeres
spindle fibers on each side shorten
New (unduplicated) chromosomes move toward the M.T.O.C.s

12. Telophase
Chromosomes stop moving when they reach the spindle poles (at the M.T.O.C.s)
Nuclear Envelope re-forms (2x)
Nucleolus re-forms (2x)
Spindle fibers disappear
Cytokinesis

13. Cytokinesis Cleavage Furrow divides the cells Cell Plate

14. Meiosis Associated with Sex! Sexual Reproduction involves 2 parents
Mixing of genetic information
Life cycles, with MEIOSIS & FERTILIZATION

15. Life Cycles
HAPLOID
GAMETIC
DIPLOID

16. Meiosis Mixing of Genetic Information Germ Cells (Sex Cells)
Reduction in Chromosome Number
Diploid  Haploid
2 Divisions
Meiosis I --- P,M,A,T
Meiosis II --- P,M,A,T
Results in 4 cells

17. Meiosis I Prophase I Metaphase I Anaphase I Telophase I
Pairing and separation of Homologous Chromosomes
Crossing Over
Independent Assortment
2n1n
VARIATION!

18. Meiosis I

19. Meiosis II Prophase II Metaphase II Anaphase II Telophase II
Separation of sister chromatids
1n1n
Results in 4 DIFFERENT cells.

20. Meiosis II

21. MEIOSIS -- Spermatogenesis

22. MEIOSIS -- Oogenesis
Stimulated by
Fertilization

23. MITOSIS vs MEIOSIS