1. Cell Division

2. Functions of Cell Division
Cell Division allows organisms to grow, repair damaged structures, and reproduce.
One cell splits into two, two into four, and so on, until a single cell becomes a multi-cellular organism.
When you have a broken bone, cell division produces new healthy bone cells that replace the damaged cells.

3. Functions of Cell Division
Some organisms reproduce simply through cell division. May single-celled organisms, such as amoebas, reproduce this way. Other organisms can reproduce when cell division leads to growth of new structures.
Ex: A cactus can grow new stems and roots. These structures can then break away from the parent plant and become a separate plant.

4. Functions of Cell Division
Many organisms reproduce when specialized cells from two different parents combine, forming a new cell. This cell then undergoes many divisions and grows into a new organism.

5. Cell Cycle
The cell cycle is the regular sequence of growth and division that cells undergo.
During the cell cycle, a cell grows, prepares for division, and divides into two new cells, which are called “daughter cells”.
The cell cycle consists of three main stages: interphase, mitosis, and cytokinesis.

6. Interphase – Stage 1 The first stage of the cell cycle is interphase.
This stage is the period before cell division. During interphase, the cell grows, makes a copy of its DNA, and prepares to divide into two cells.
Early during interphase, a cell grows to its full size and produces the organelles it needs.

7. Interphase Ex: plant cells make more chloroplasts.
All cells make more ribosomes and mitochondria.
Cells also make more enzymes, substances that speed up chemical reactions in living things.

8. Interphase
Next, the cell makes an exact copy of the DNA in its nucleus in a process called replication. Within the nucleus, DNA and proteins form threadlike structures called chromosomes. At the end of replication, the cell has two identical sets of chromosomes.

9. Interphase
Once the DNA has replicated, preparation for cell division begins. The cell produces structures that will help it divide into two new cells. In animal cells, a pair of centrioles is duplicated.
At the end of interphase, the cell is ready to divide.

10. Mitosis – Stage 2
Once interphase ends, the second stage of the cell cycle begins.
During mitosis, the cell’s nucleus divides into two new nuclei, and one set of DNA is distributed into each daughter cell.
Scientists divide mitosis into four parts, or phases: prophase, metaphase, anaphase, and telophase.

11. During prophase, the chromosomes condense into shapes that can be seen under a microscope.
You can see that a chromosome consists of two rod-like parts, called chromatids. Each chromatid is an exact copy of the other, containing identical DNA. The centromere holds the chromatids together until they move apart later in mitosis.
Prophase

12. Metaphase
Each chromosome attaches to a spindle fiber at its centromere.
Notice that the nucleus is missing and the chromosomes moved to the center of the cell.

13. The centromere of each chromosome splits, pulling the chromatids apart.
Each chromatid is now called a chromosome. These chromosomes are drawn by their spindle fibers to opposite ends of the cell. The cell stretches out.
Anaphase

14. Telophase is the fifth and final phase of mitosis, the process that separates the duplicated genetic material carried in the nucleus of a parent cell into two identical daughter cells.
Notice that the nuclei are forming around the chromatids, spindle fibers have disappeared, and the cell is pinched in around its middle.
Telophase

15. Cytokinesis – Stage 3
The final stage of the cell cycle is called cytokinesis, completes the process of cell division.
During cytokinesis, the cytoplasm divides and the structures are then distributed into each of the new cells.

16. Cytokinesis
Cytokinesis usually starts about the same time as telophase. When cytokinesis is complete, each daughter cell has the same number of chromosomes as the parent cell. At the end of cytokinesis, each cell enters interphase, and the cycle begins again.