1. (1.2) Cell Division (p22-27)

2. Cell Division Cells must divide to survive. There is a limit to how large a cell can grow. If the amount of material in a cell is too large the cell dies.

3. Cell Division When a cell divides - two new cells are created - each cell is identical to the original cell The set of instructions each cell inherits is stored in a unique molecule called DNA (deoxyribonucleic acid).

4. DNA DNA in the nucleus of the cell contains the hereditary material. DNA molecules have a shape like that of a ladder. To fit inside the nucleus DNA forms compact coiled threads called chromatin. To reproduce the chromatin packs together to form chromosomes. Chromosomes pass on hereditary information when a cell divides.

5. DNA Chromatin are thin threads of DNA. If the DNA in one of your cells is uncoiled it would be 2 m long! Chromatin DNA

6. Cell Cycle The series of events in the life of a cell is called the cell cycle. Two main stages: i) growth - called interphase ii) division - consisting of mitosis and cytokinesis

7. Growth Stage During interphase the cell: -grows -carries out its usual functions -makes copies of its DNA and organelles to prepare for cell division Most cells spend most of their lives in interphase. Interphase ends when a cell begins to divide.

8. Division Stage Two phases of cell division: 1.Mitosis - the contents of the nucleus separate into 2 identical copies. 2. Cytokinesis - cytoplasm and organelles divide into 2 identical, separate copies - each cell now starts its own cell cycle

9. Cell Division - It’s Important Through cell division livings things undergo three important functions: i) growth ii) maintenance iii) repair

10. Classwork Text p 23 LC #1-3 p 25 LC #1-3 p 27 LC #1,3 Quiz: Next class on section (1.1) - cell parts, diffusion and osmosis