1. The Cell Cycle and
Asexual Reproduction
(Mitosis) 1

2. How do little elephants grow up to be BIG elephants?

3. Why do animals shed their skin?

4. The Cell Cycle
The process of asexual reproduction in Eukaryotes is called the CELL CYCLE
Sometimes just called Mitosis
Mitosis specifically refers to the division of the nucleus
Cell Cycle stages: G1, S, G2, M, and Cytokinesis
G1 S and G2 are collectively called INTERPHASE
M phases stands for Mitosis phase; it includes four phases of its own
Encompasses the entire life of the cell
Prokaryotes have a special name for their cell cycle called “binary fission” since “mitosis” is just for a nucleus

6. The Cell Cycle is used for
1. Quick reproduction – offspring will be genetically IDENTICAL or clones (unicellular organisms only) 2. Growth (multicellular organisms only) 3. Repair and Replacement of old cells (multicellular organisms only) Cell Cycle Animation -

7. Forms of DNA
Every living thing has at least one piece of DNA, but most multicellular eukaryotes have many pieces. The number depends on the species. (Ex: Humans have 46)
DNA in the nucleus can be found in various forms
chromatin: uncoiled DNA (noodles)
chromatid: single, coiled piece of DNA, 1/2 a chromosome (dreadlock)
chromosome: X-shaped pair of duplicate DNA pieces held together by a centromere

8. DIPLOID vs HAPLOID
Most eukaryotic species are DIPLOID meaning they have at least two pieces of DNA per trait.
One piece comes from the mother and the other comes from the father.
These pieces code the same trait, but they may not be the exact same instructions. For example, one may say BLUE eyes while the other says BROWN. These means they are HOMOLOGOUS (same, but not EXACTLY the same)
Homologous pair: set of “matching” chromosomes (one from each parent) that may have different variations of the same genetic trait (blue vs brown eyes)
Which piece is actually used depends on genetics. More on that in a later unit.
Advantageous to be diploid because you have a BACKUP in case one piece is damaged.
Some species or special cells do NOT contain these pairs. They only have one piece of DNA for each trait, meaning they are HAPLOID
These cells are either simple (fungi) or used for sexual reproduction only
Note: Mitosis always makes DIPLOID cells. Most NORMAL (non-sex) cells are DIPLOID

9. Mitosis vs Meiosis
The purpose of Mitosis is to clone the parent cell. Each new cell created through mitosis is diploid and IDENTICAL to the parent cells.
Later we will learn about Meiosis, which makes half cells for the purpose of sexual reproduction

10. Cell Cycle Stages

11. Interphase Cell is doing its “day job” and maintaining homeostasis
G1 – grow/maintain homeostasis
S – synthesis, copy all the DNA/maintain homeostasis
G2 – prepare to divide/maintain homeostasis
Interphase is the longest phase of the cycle. It can last for hours, days, or even weeks.
Optional Phase – G0: some cells enter G0 and NEVER divide; their “day job” is too important; ex: nerve cells (this is why spinal cord injuries do not heal)
Cell looks like a normal cell

12. Interphase (G1, S, and G2) Plant Cell Animal Cell
Photographs from:

13. Mitosis - Prophase
Homeostasis is briefly paused for M phase; other cells will pick up the slack
Prophase is the first stage of M phase, aka mitosis
Cell prepares to divide by coiling the DNA into chromosomes and getting rid of the nucleus; spindle fibers form
Recognized by the visible chromosomes

14. Prophase Plant Cell Animal Cell
Photographs from:

15. Mitosis - Metaphase
The coiled chromosomes line up single file in the middle of the cell attached to the spindle fibers
Recognized by the line of chromosomes in the MIDDLE

16. Metaphase Plant Cell Animal Cell
Photographs from:

17. Mitosis - Anaphase
Remember – each X shaped chromosome is made of DUPLICATED DNA! Each new cell will need one piece, so in anaphase…
The chromosomes are pulled apart by the spindles and dragged to opposite sides of the cell
Recognized by the APART

18. Anaphase Plant Cell Animal Cell
Photographs from:

19. Mitosis - Telophase
Remember – mitosis only refers to the division of the NUCLEUS
Two new nuclei form around the DNA on the opposite sides; spindle disappears
Reverse of prophase
Recognized by the two visible nuclei

20. Cytokinesis This is NOT a part of mitosis!
As telophase splits the nuclei, cytokinesis splits the rest of the cell
Animal cells – cleavage furrow (pinch the membrane until the cell splits
Plant cells – cell plate (new cell forms in between the two cells)

21. Telophase and Cytokinesis
Plant Cell
Animal Cell
Photographs from:

22. Animal Cell Mitosis
Interphase                                                             
Prophase                                                             
Metaphase                                                             
Anaphase                                                             
Telophase                                                             

23. Plant Cell Mitosis
Interphase                                                             
Prophase                                                             
Metaphase                                                             
Anaphase                                                             
Telophase                                                             

24. IPMATC REMEMBER! Interphase Prophase Metaphase Anaphase Telophase
Cytokinesis
IPMATC
A mnemonic to help remember the stages of mitosis.
I Play Mudpie At The Creek

25. What Phase?

26. What Phase?

27. What Phase?

28. What Phase?