1. Cell Division

2. Types of Cell Reproduction
Asexual reproduction involves a single parent cell dividing to make 2 new daughter cells that are genetically identical to the parent.
Examples: Mitosis & Binary fission
Sexual reproduction involves cells from two parents (egg & sperm) joining to make a new cell (zygote) that is NOT identical to the original cells.
Example: Meiosis

3. Cell Division All cells are derived from pre-existing cells.
Cell division differs in prokaryotes (bacteria) and eukaryotes (protists, fungi, plants, and animals).

4. Cell Division in Prokaryotes
Prokaryotes reproduce asexually by dividing into 2 identical cells by the process of binary fission.
Single chromosome makes a copy of itself.
Cell wall forms between the chromosomes dividing the cell.
Parent cell
Chromosome replicates
Cell splits
2 identical daughter cells

5. Prokaryotic Cell Undergoing Binary Fission

6. Cell Division in Eukaryotes
Two types of cell division:
Mitosis results in new cells that are identical to the original cell.
Meiosis occurs during the formation of gametes (haploid reproductive cells).
More on this topic later.

7. Mitosis and Cytokinesis
In eukaryotes, cell division occurs in two major stages.
The first stage, division of the cell nucleus, is called mitosis.
The second stage, division of the cell cytoplasm, is called cytokinesis.
Note: The following process is how all human cells are made except reproductive (sperm and egg) cells!

8. Mitosis
Mitosis follows Interphase, so the DNA is already duplicated.
Biologists divide the events of mitosis into four phases: (PMAT)
Prophase
Metaphase
Anaphase
Telophase
Cell Cycle
Remember:
Pitt Made Another Touchdown

9. Most eukaryotic cells go through a regular cycle of interphase, mitosis and cytokinesis. Mitosis has four phases: Prophase, Metaphase, Anaphase and Telophase. The events shown here are typical of animal cells.
Mitosis

10. Chromosomes (paired chromatids)
Spindle forming
Prophase
Prophase
Chromosomes (paired chromatids)
Centromere
Most eukaryotic cells go through a regular cycle of interphase, mitosis and cytokinesis. Mitosis has four phases: Prophase, Metaphase, Anaphase and Telophase. The events shown here are typical of animal cells.
Pitt

11. Pitt Prophase Prophase is the longest phase of mitosis.
Spindle
forming
Prophase
Prophase is the longest phase of mitosis.
The centrioles separate and take up positions on opposite sides of the nucleus.
Centromere
Chromosomes
(paired chromatids)
Pitt

12. Pitt Prophase The centrioles lie in a region called the centrosome.
The centrosome helps to organize the spindle, a fanlike microtubule structure that helps separate the chromosomes.
Centriole
Spindle
forming
Centromere
Chromosomes
(paired chromatids)
Pitt

13. Pitt Prophase Chromatin condenses into chromosomes.
The centrioles separate and a spindle begins to form.
The nuclear membrane breaks down.
Centriole
Spindle
forming
Centromere
Chromosomes
(paired chromatids)
Pitt

14. Metaphase
Centriole
Spindle
Centriole
Metaphase
Made

15. Made Metaphase The chromosomes line up across the center of the cell.
Spindle fibers attach to the centromere of each chromosome.
Centriole
Made
Spindle

16. Individual chromosomes
Anaphase
Individual chromosomes
Anaphase
Another

17. Anaphase
The sister chromatids separate into individual chromosomes.
The chromosomes continue to move until they have separated into two groups at opposite ends of the cell.
Individual
chromosomes
Another

18. Nuclear envelope reforming
Telophase
Nuclear envelope reforming
Telophase
Touchdown

19. Telophase
Chromosomes gather at opposite ends of the cell and lose their distinct shape.
Spindle fibers disassemble.
New nuclear membranes form around each cluster of chromosomes.
Cleavage furrow in animal cell
Touchdown

20. Cytokinesis
Cytokinesis

21. Cytokinesis
During cytokinesis, the cytoplasm pinches in half.
Each daughter cell has an identical set of duplicate chromosomes.
Each daughter cell is smaller than parent cell and must grow in size to become mature cells during G1 of Interphase.

22. Cytokinesis: Animals vs. Plants
In plant cells, a structure known as the cell plate forms midway between the divided nuclei.
In animal cells, a structure called cleavage furrow forms.
Cleavage Furrow in Animal Cell
Cell Plate in Plant Cell
Cell wall
Cell plate

23. Stages Of Mitosis Remember: Pitt Made Another Touchdown Mother cell
Interphase
Nucleus with un-condensed chromosomes
Prophase
Condensed chromosomes
Equator of the cell
Metaphase
Disappearing nuclear membrane
Poles of the cell
Anaphase
Two daughter cells
Mitotic spindle
Telophase & Cytokinesis
Remember:
Pitt Made Another Touchdown

24. Control of Cell Division
A cell spends most of its time in interphase.
What tells the cells to exit interphase and begin dividing?
The cell cycle is regulated by proteins.
Proteins regulate the cell cycle by allowing the cell cycle to proceed only when certain processes have happened inside the cell.
Proteins also respond to events outside the cell and direct cells to speed up or slow down the cell cycle.
There are three main checkpoints that act as “traffic signals” for the cell to divide or not to divide.

25. Control of Cell Division
Cell growth (G1) checkpoint – controls whether the cell will divide
DNA synthesis (G2) checkpoint – makes sure DNA was copied properly
Mitosis checkpoint – signals tell the cell to exit mitosis

26. When Control Is Lost: Cancer
Certain genes contain the information necessary
to make the proteins that regulate cell growth and
division.
If one of these genes is mutated, the protein may
not function, and regulation of cell growth and
division can be disrupted.
Cancer, the uncontrolled growth of cells, may result.
Although mutations can occur spontaneously,
many occur as a result of environmental influences.
Examples: tobacco products, exposure to ultraviolet radiation, certain viruses
If mitosis is not controlled, unlimited cell division occurs causing cancerous tumors.
Cancer cells may break loose from tumors and spread throughout the body, disrupting normal activities and causing serious medical problems or even death.
Cancer Cells

27. Cancer Video Clips https://www. youtube. com/watch