1. Cellular Reproduction
Mitosis & Meiosis

2. Chromosome Structure
Chromatin – Thin, uncoiled strands of DNA & proteins (histones)
Chromosomes – Rod-shaped structures composed of coiled strands of DNA & proteins.
Chromosomes are made up of two sister chromatids held together at a central point called a centromere.

3. Chromosomes

4. The Cell Cycle G1 Period – Cell growth S Period – DNA Replication
G2 Period – Rapid cell growth
Mitosis – Cell division
Cytokinesis – Cytoplasmic division

5. The Cell Cycle

6. Interphase Comprised of the G1, S, & G2 periods.
A period of preparation for mitosis.

7. The Phases of Mitosis Period of nuclear division Prophase Metaphase
Anaphase
Telophase

8. Prophase Chromatin coils to form chromosomes.
Nucleolus & nuclear membrane disappear.
Spindle fibers begin to develop.
Kinetochore fibers (pole to chromosomes);
Polar fibers (pole to pole)
Formation of asters.
Asters: Protein fibers that radiate from each pole.

9. Metaphase Chromosomes move to the equator/center of the cell.
Metaphase plate formation

10. Anaphase Centromeres of each pair of chromatids divide.
Chromatids separate & move to opposite poles.

11. Telophase Centrioles & spindle fibers disappear
Chromatids unwind to form chromatin
Nuclear membrane & nucleolus reappear

12. Cytokinesis The division of the cytoplasm
ANIMAL CELL – cleavage furrow
PLANT CELL – cell plate formation
Cell Plate

13. Phases of Mitosis

14. Meiosis
Process of nuclear division that reduces chromosome number in half.
Used to create germ cells (gametes)
Two divisions
Meiosis I
Meiosis II

15. Meiosis I Prophase I Nuclear membrane/nucleolus disappear
Crossing Over
Prophase I
Nuclear membrane/nucleolus disappear
Chromosomes form from chromatin
Homologous chromosomes line up together in process called synapsis (form tetrads)
Crossing over occurs (Genetic Recombination)
Spindle fibers form.
Metaphase I
Homologous chromosomes move to equator.
Anaphase I
Homologous chromosomes separate & move to poles.
Telophase I
Cytoplasm divides (forms 2 daughter cells)
Nuclear membrane & nucleolus reappear

16. MeiosisII Most like Mitosis Prophase II Metaphase II Anaphase II
Click**
Most like Mitosis
Prophase II
Nuclear Membrane & nucleolus disappear
Metaphase II
Chromosomes line up on equator
Anaphase II
Chromatids separate
Telophase II
Nuclear membrane & nucleolus reappear
Chromosomes uncoil

17. Karyotype

18. Formation of Gametes – Result of Meiosis
Spermatogenesis
Occurs in males.
Four sperm cells are formed.
Oogenesis
Occurs in females.
I egg (ovum) formed.
3 polar bodies formed, but eventually disintegrate.

19. Chromosome Numbers
Chromosomes appear in pairs in all sexually reproducing organisms.
Called homologous chromosomes
Same shape & same size
Diploid number (2N) – A cell containing both chromosomes of a homologous pair.
Haploid number (1N) – A cell containing one chromosome of a homologous pair.

20. Diploid vs. Haploid Cells

21. Mitosis Production vs Meiosis
Somatic cells are body cells
Formed via ________________
Somatic cells are (diploid/haploid)
Germ cells are reproductive/sex cells (gametes)
Germ cells are (diploid/haploid)

22. Mitosis vs. Meiosis