Do Now: Take the worksheet from the front of the room Homework: 1. Read pages 61-68 2. Cell definitions

Cell Division (2.3) Cells reproduce by dividing 1. In order to divide, cells need to duplicate their structures (organelles) or divide the structures equally between the two new cells. 2. The regular sequence of growth and division is called the cell cycle. 3. The cell cycle is divided into a series of phases. 4. At the end of the cell cycle, one “parent” cell becomes two “daughter” cells.

B. Interphase 1. Interphase is the period before cell division occurs, the cell grows to its mature size, makes a copy of its DNA and prepares to divide into two cells. 2. The cell doubles in size and produces all structures needed to carry out cell division 3. The cell makes a copy of its DNA through a process called replication. Replication of the DNA is very important because each daughter cell needs a complete set of DNA to survive.

Mitosis - Cell Division During mitosis, the cell’s nucleus divides into two new nuclei. One copy of the DNA is distributed into each of the two daughter cells.

C. Mitosis 1. the chromatin in the nucleus condenses to form chromosomes. 2. structures called spindle fibers form a bridge between the ends of the cells 3. the nuclear membrane breaks down 4. the chromosomes line up across the center of the cell 5. each chromosome attaches to a spindle fiber at its centromere, which holds its chromatids together

6. the centromeres split, the two chromatids separate 7. one chromatid moves along the spindle fiber to one end of the cell, the other chromatid moves to the opposite end 8. the cell becomes stretched out as the opposite ends pull apart 9. the chromosomes begin to stretch out and lose their rod like appearance 10. this occurs in two regions at the ends of the cell 11. a new nuclear membrane forms around each region of chromosomes

D. At the end of Mitosis, cytokinesis occurs 1. Cytokinesis is the division of the cytoplasm 2. At the end of cytokinesis, the two new daughter cells are exactly the same as the original parent cell.

- Cell Division The Cell Cycle

Cell Cycle Activity - Cell Division Click the Active Art button to open a browser window and access Active Art about the cell cycle.

Length of the Cell Cycle - Cell Division Length of the Cell Cycle How long does it take for a cell to go through one cell cycle? It all depends on the cell. A human liver cell, for example, completes one cell cycle in about 22 hours, as shown in the graph. Study the graph and then answer the following questions. 1.

Length of the Cell Cycle - Cell Division Length of the Cell Cycle How long does it take for a cell to go through one cell cycle? It all depends on the cell. A human liver cell, for example, completes one cell cycle in about 22 hours, as shown in the graph. Study the graph and then answer the following questions. What do the three curved arrows outside the circle represent? In what stage of the cell cycle is the wedge representing growth? In human liver cells, how long does it take DNA replication to occur? In human liver cells, what stage in the cell cycle takes the longest time?

Length of the Cell Cycle - Cell Division Length of the Cell Cycle Reading Graphs: What do the three curved arrows outside the circle represent? The longest curved arrow represents the cell’s interphase; the shortest represents cytokinesis; and the middle one represents mitosis.

Length of the Cell Cycle - Cell Division Length of the Cell Cycle Reading Graphs: In what stage of the cell cycle is the wedge representing growth? Interphase

Length of the Cell Cycle - Cell Division Length of the Cell Cycle Interpreting Data: In human liver cells, how long does it take DNA replication to occur? 10 hours

Length of the Cell Cycle - Cell Division Length of the Cell Cycle Drawing Conclusions: In human liver cells, what stage in the cell cycle takes the longest time? Interphase