1. Basic Cell Biology Topic 3202C, 3025G, 3025H Melinda Klockziem
Mitosis and Meiosis
Basic Cell Biology
Topic 3202C, 3025G, 3025H
Melinda Klockziem

2. Mitosis

3. How do cells reproduce?
Mitosis -- the cells divide to produce two identical cells.
Genetic material in both is identical
End up with two diploid cells
Mitosis is necessary for growth and maintenance.

4. Stages of mitosis 1. Interphase The cell doubles its DNA
Nucleoli and nuclear membrane present

6. Stages of mitosis 2. Prophase Sister Chromatids shorten and thicken
Chromosomes visible
Nuclear membrane disappears
Chromosomes have “X” shape joined at the centromere

8. Stages of mitosis 3. Metaphase
Sister chromatids line up along equator of the cell
Attach to spindle fibers which act a guide to separate the sister chromatids

10. Stages of mitosis 4. Anaphase Sister chromatids separate
Sister chromatids move to opposite ends of the cell

12. Stages of mitosis 5. Telophase Nuclear membranes reform
Two new cells are separated
Cytokinesis occurs

14. Animation of Mitosis
Cell Alive Website

15. Cancer and Mitosis Mitosis is necessary, but…
Uncontrolled mitosis is cancer.
Cancer cells divide without control.
Cancer cells create a mass in tissues or organs.
Two types of Cancer
Benign
Malignant

16. Mitosis Yarn Lab

17. Meiosis

18. Background Information
Chromosome Numbers
Haploid or N
Humans 23 Haploid number (N)
Chromosomes are in pairs
Humans have a total of 46 chromosomes or 2N (diploid)
Meiosis reduces 2N to N
Thus when sperm and ova meet and combine at fertilization the resulting embryo will have 2N

19. How else do cells reproduce?
Meiosis is the reproduction of animal sex cells
Ova and sperm
Happens in two stages
Two divisions of the cell compared to only one division in mitosis
End up with four haploid cells

20. Stages of Meiosis I Prophase I Chromosomes thicken and becomes visible
Chromosomes are present in homologous pairs

21. Stages of Meiosis I Metaphase I
Homologous pairs line up on the axis of the dividing cell opposite from each other.

22. Stages of Meiosis I Anaphase I
Homologous pairs of chromosomes leave each other and are pulled towards opposite poles by spindle fibers

23. Stages of Meiosis I Telophase I The cells physically divide
Each daughter cell now contains one chromosome from each pair
Reduction Division
Number of chromosomes is reduced from diploid to haploid.

24. Stages of Meiosis II Prophase II Chromosomes still duplicated

25. Stages of Meiosis II Metaphase II
Sister chromatids line up on the axis of the cell.

26. Stages of Meiosis II Anaphase II
The sister chromatids are pulled apart at the centromere by spindle fiber

27. Stages of Meiosis II Telophase II Nuclear membrane reforms
Each of the four final haploid cells or gametes contain one strand from the original homologous pair of chromosomes.