1. Unit 4: Reproduction Chapter 5
Mitosis is the basis of asexual reproduction

2. Cell Cycle & Development
It is necessary for cells to divide, producing more cells, as an organism develops.
Cells die and need to be replaced. Cells that take a lot of wear and tear, including skin cells, stomach cells and intestinal cells need to be replaced.
The Cell Cycle ensures that body cells are replaced and the overall health of the organism is maintained.

3. Cell Cycle Stages
Cell Cycle: is a series of three stages in the life of a cell. The cycle involves cellular division to produce more identical cells.
The 3 stages of the Cell Cycle are:
Interphase
Mitosis
Cytokinesis

4. Stage 1: Interphase Stage 1: Interphase
Interphase: is the first and longest stage of the cell cycle. During this stage the cell carries out its various functions and prepares for division.
During Interphase the cell doubles all of its material, including its DNA in preparing for division. The process of doubling the amount of DNA in interphase is called Replication.

5. Stage 2: Mitosis
Mitosis: the second, and usually the shortest stage of the cell cycle, involves the division of a cell’s nucleus producing two identical daughter cells.

6. Stages of Mitosis Mitosis involves 4 distinct stages or steps.
The 4 stages of Mitosis, in order, are:
Prophase
Metaphase
Anaphase
Telophase

7. Prophase (Early) Stage 1: Early Prophase
Replicated chromosomes pair up into X-shaped structures
Nuclear membrane breaks down
Spindle fibres (from Centrioles) begin to stretch across the cell

8. Prophase (Late) Stage 1: Late Prophase Centrioles are on opposite
(poles) of the cell and
spindle fibres spread,
attaching to Centromere of
the Sister Chromatids.

9. Metaphase
The fibre (protein) spindles pull the x-shaped chromosomes into a straight line across the middle of cell.

10. Anaphase
Spindle fibres contract, pulling each half of the sister chromatid towards each centrioles.
At this point, each chromatid is considered a chromosome.

11. Telophase
Spindle Fibres break down and a nuclear membrane forms around each set of chromosomes.
The final stage of cytokinesis is to divide the cell into two equal but separate parts.

12. Stage 3: Cytokinesis
Cytokinesis: is the final stage of the cell cycle. Once mitosis is complete, the cell membrane pinches together and the cell divides into two identical daughter cells.

13. The products of Mitosis
Mitosis results in one parent cell dividing to produce two identical daughter cells which have the same number of chromosomes as the parent cell.
Think about it …
How many brain cells originally underwent cell division to produce 24 brain cells?
A cell divides by mitosis once every two hours. How many of these cells will be produced after an 8 hour period?

14. Checkpoints in the Cell Cycle
Special proteins at checkpoints monitor cell activities and send this information along to the nucleus.
At each checkpoint, the nucleus instructs the cell whether or not to divide.
A cell will stop undergoing division if:
Not enough nutrients for cell growth
Replication of DNA did not occur
DNA is damaged

15. Asexual Reproduction
Asexual Reproduction: a method of reproduction involving only ONE parent, producing identical offspring to the parent.
Cloned organisms are produced through asexual reproduction.

16. Methods of Asexual Reproduction
Methods of asexual reproduction include:
Binary fission
Budding
Fragmentation
Vegetative reproduction
Spore formation

17. Binary fission
Binary fission: a single one-celled parent replicates its genetic material and divides into two equal parts.
This method is the only method of reproduction for some types of bacteria.
Amoebas reproduce by binary fission. Algae and protozoa also reproduce by binary fission.

18. Budding
Budding: part of a cell pushes outward to form an outgrowth or bud that may detach from the parent cell.
Unicellular yeasts, and multicellular organisms such as the hydra and sponges reproduce by budding.

19. Fragmentation
Fragmentation: a fragment, a piece of an organism broken off as a result of injury, develops into a clone of its parent.
Some species of sea stars reproduce asexually by Fragmentation. Some plant also reproduce this way.

20. Vegetative Reproduction
Vegetative Reproduction: special cells, usually in plant stems and roots, divide repeatedly to eventually form a plant that is identical to the parent.
Tulips, Daffodils, Potato Sprouts (“eyes”), and Strawberry stem runners produce plants this way.

21. Spore Formation
Spore Formation: reproducing asexually by forming single celled spores.
Spores: a reproductive cell that grows into a new individual by mitosis. Spores can be carried easily by the actions of wind and water.
Some plants, including ferns and mosses reproduce by spore formation. Mold also can reproduce this way.