1. A process called MITOSIS
Mitosis Basics
How does a single cell (the fertilized egg) become a multicellular baby?
A process called MITOSIS

2. 2 identical diploid cells
Mitosis is the process of creating two genetically identical daughter cells from one pre-existing parent cell. These daughter cells are for growth or for the replacement of dead cells.
The circular diagram on the lower left shows the life cycle of the cell. In the G1, S, and G2 phases, the cell prepares for mitosis by duplicating chromosomes and other cell parts. The phases of mitosis occur in M, ending in cytokinesis, the final division into two genetically identical cells.
2 identical diploid cells

3. Mitosis
Mitosis results in a parent cell dividing into two daughter cells.
The genetic information within each of these daughter cells
is identical.

4. Mitosis Interphase The period between cell divisions.
During this time, chromosomes replicate.

5. Mitosis Prophase Chromosomes begin to condense.
Each chromosome is two identical copies called chromatids.
Spindle begins to form from the centrioles.

6. Mitosis Prometaphase
The centrioles are now at opposite ends of the cell.
The spindle fibers from both of the centrioles
attach to each one of the chromosomes.

7. Mitosis Metaphase The chromosomes line up on the metaphase plate.
The fibers begin to tug each chromosome toward
opposite ends of the cell.

8. Mitosis Anaphase The fibers pull the chromatids toward opposite
ends of the cell.

9. Mitosis Telophase
The chromatids arrive at the opposite ends of the cell
New nuclear membranes form.
Mitosis is now complete.

10. Mitosis End of Cytokinesis
The rest of the cell divides.
Cytokinesis, the division of the cell's cytoplasm,
is now complete.

11. Sockosome Activity Mitosis

12. Meiosis Basics A process called MEIOSIS
For sexual reproduction to occur, each gamete has to have half the normal number of chromosomes.
How do we get from the diploid somatic cell to the haploid gamete?
A process called MEIOSIS
Bullet 1: We are now ready to connect the process for gamete formation that students followed in the Reebops activity to MEIOSIS.
Bullet 2: In animals, the cells that give rise to gametes are called germline cells. Plants, in contrast to animals, form germ cells (sperm and eggs) from somatic tissues.
Meiosis consists of two cell divisions. In the first cell division, shown with a yellow background, one diploid cell divides to form two diploid daughter cells. These daughter cells are not identical because of a process called crossing over in which duplicated chromosomes (called sister chromatids) swap genes. This genetic recombination is an important source of variation. In the second cell division, diploid cells divide (without duplicating their DNA) to become haploid gametes, or sex cells.
1 diploid cell
2 diploid cells
4 haploid cells

13. Mitosis vs Meiosis http://www.pbs.org/wgbh/nova/baby/divide.html
While the purpose of this lesson is not to provide a detailed discussion of the phases of mitosis and meiosis, this animation, which which provides a step-by-step comparison of meiosis and mitosis, allows you to point out the highlights.
To view the animation, go to and choose: Go to "Mitosis vs. Meiosis”
Your computer will need to have a Flash plugin. It's probably already there with newer browsers. You can also view a non-flash version at

14. Mitosis Meiosis Interphase Interphase I
Identical to Mitosis
The period between cell divisions.
During this time, chromosomes replicate.

15. Synapsis Homologous chromosomes (identical maternal and
paternal set) pair all along their length.
Synapsis allows crossing over.

16. Chiasmata Crossing over allows exchange of information between
sister chromatids.
Chiasmata created by crossing over holds the two sister
chromatids together during metaphase I.

17. Mitosis Meiosis Prometaphase Prometaphase I
Spindle fibers from each centriole
attach to one chromosome of a
matching chromosome pair.

18. Mitosis Meiosis Metaphase Metaphase I
The chromosome pairs line up on either
side of the metaphase plate.
Maternal and paternal chromosomes randomly
segregate to the two halves

19. Mitosis Meiosis Anaphase Anaphase I
Half of the chromosomes move toward one end of
the cell, the other half, to the other end.
The chromosomes' sister chromatids do not
separate as they do in mitosis.

20. Mitosis Meiosis Telophase Telophase I
The chromatids arrive at the opposite ends
of the cell
New nuclear membranes form.

21. Mitosis Meiosis End of Cytokinesis
The rest of the cell divides.
Cytokinesis is now complete.

22. Meiosis Second Cell Division Interphase II
The chromosomes do not replicate during this phase,
as they do in mitosis and interphase I in meiosis.

23. Meiosis Second Cell Division Prophase II
The chromosomes condense and spindles form.
Unlike prophase I, the chromosomes do not attach to
the nuclear membrane in order to exchange
genetic information.

24. Meiosis Second Cell Division Prometaphase II
As in mitosis prometaphase, fibers from both ends
of the cells attach to each one of the four
chromosomes.

25. Meiosis Second Cell Division Metaphase II
As in mitosis metaphase, (and unlike meiosis metaphase I),
fibers from the centrioles begin to pull on each one
of the chromosomes from both directions.

26. Meiosis Second Cell Division Anaphase II
As in anaphase in mitosis (and unlike anaphase I in meiosis),
the fibers pull the chromatids apart and toward
opposite ends of the cells.

27. Meiosis Second Cell Division Telophase II
The chromatids arrive at the opposite ends of the cell
New nuclear membranes form.
Meiosis is now complete.

28. Meiosis Second Cell Division End of Cytokinesis
The rest of the cell divides.
Cytokinesis is now complete.

29. Sockosome Activity Meiosis

30. What are the unique features of Meiosis ?

31. Meiosis is necessary for Sexual Reproduction
Meiosis is necessary for Sexual Reproduction. How is sexual reproduction important for evolution?