1. The cell cycle Cytokinesis Mitosis
Second phase of growth, further synthesis of organelles occurs, chromosomes start condensing
Nuclear division
Cytokinesis
Cytoplasmic division
First phase of growth, the cell grows and develops, and additional organelles are synthesised, the nucleus directs protein synthesis.
Synthesis of DNA, the DNA of the chromosomes is replicated

2. Interphase Centriole Chromosome Nucleolus
is long and thin, cannot be seen under the light microscope
Cell synthesizes more cytoplasm and organelles, chromosomes replicate, cell builds up large store of energy
Nucleolus

3. Nuclear division
MITOSIS

4. Prophase Chromosome Nucleolus
Shortens and condenses, becomes visible under the light microscope
Nucleolus
Gradually disappears

5. Prophase Centrioles move towards opposite poles of the cell Chromatid
Centromere

6. Prophase Centriole Nuclear membrane Sister chromatids
Microtubules extend from here towards the equator of the cell to form the spindle
Nuclear membrane
Begins to break down
Sister chromatids

7. Metaphase Spindle pole Spindle fibre Spindle equator
Centromere becomes attached to a spindle fibre and moves to the equatorial plane
Spindle equator
Chromosomes line up at the equator of the spindle

8. Anaphase Daughter chromosome
Centromere divides and the daughter chromosmes move to opposite poles with centromere leading

9. Telophase Nuclear membrane
Surrounds daughter chromosomes
Chromosomes uncoil and gradually become invisible under light microscope
Nucleolus
reforms

10. CYTOKINESIS
Division of the cytoplasm

11. Animal cell
Cell membrane invaginates at the mid point of the cell dividing the cell into two, cells are diploid (2N) and are identical to each other

12. Plant cell
Tiny vesicles containing cell wall materials coalesce to form the cell plate
Cell plate extends outward to the cell wall and separates cell into two

13. Nuclear division
MEIOSIS

14. Meiosis I

15. Prophase I Pairing of homologous chromosomes
maternal and paternal chromosomes come together and lie close to each other
Bivalent

16. Prophase I
Sister chromatids separate and become visible, they are held together by the centromere

17. Prophase I
Crossing over occurs between chromatids of homologous chromosomes
Chiasma

18. Metaphase I Centromere becomes attached to individual spindle fibre
Chromosomes lie at the equator of the spindle with members of each homologous pair facing opposite poles

19. Anaphase I
Members of each homologous pair move towards opposite poles

20. Telophase I Nuclear membrane reforms around the chromosomes
Cell divides into two

21. Prophase II
Nuclear membrane disappearing

22. Metaphase II
Chromosomes attached to spindle fibres by their centromere, line up at the equator of the spindle

23. Anaphase II
Centromeres divide and separate, pulling the sister chromatids to the opposite poles

24. Telophase II
Nuclear membrane forms around the chromosomes

25. Interphase
Four haploid (N) daughter cells are produced

26. Comparison between mitosis and meiosis
Pairing of homologous chromosomes No
Yes
Crossing over No
Yes
Anaphase
Sister chromatids separate during anaphase
Homologous chromosomes separate during anaphase I, sister chromatids separate during anaphase II.
Number of divisions involved
One
Two
Daughter cells
Two diploid (2N) daughter cells, they are identical
Four haploid (N) daughter cells, they are non-identical
Occurrence
During growth, asexual reproduction
Production of gametes for sexual reproduction

27. References
Clegg C.J., Mackean D.G., Advanced Biology: principles and applications
Enger/Ross, Concepts in Biology

28. CROSSING OVER - exchange of genetic material between non-sister chromatids
Join with broken fragments of non-sister chromatid i.e. exchange of genetic material occurs
Non-sister chromatids overlap
Once overlap, they break

29. Crossing over - Chiasma
Chiasmata have two functions: (1) hold the homologous chromosomes together as they move to the equator of the spindle (2) allow exchange of genetic materials between homologous chromosomes giving rise to genetic variations in the offspring