1. Mitosis and Meiosis Lesson 3.2 : Cell Division is part of the cell cycle Lesson 4.3: Meiosis is a special form of cell division Science Ms. Curd

2. 3.2: The cell cycle includes interphase and cell division All living things live, grow, reproduce, and die in a process called a life cycle. Cell Cycle: the normal sequence of development and division of a cell. Cell cycle consists of two main phases: interphase & mitosis/cytokinesis

3. Interphase Part of the cell cycle during which a cell is not dividing. The cell grows to about twice the size it was when first produced. The cell engages in normal activities: transporting materials in and transporting wastes out; cellular respiration occurs providing energy to the cell It duplicates its DNA exactly

4. Cell Division Phase Mitosis: part of the cell cycle during which the nucleus divides Cytokinesis: the divison of the parent cell’s cytoplasm; occurs immediately after mitosis Results: the original (parent cell) cell splits into two genetically identical daughter cells

5. Mitosis Steps 1. Prophase: Nuclear membrane disappears; Chromosomes form 2. Metaphase: Chromosomes line up in the middle of the cell 3. Anaphase: Chromatids split resulting in two separate identical chromosomes 4. Telophase/Cytokinesis: nuclear membrane forms around each group of chromosomes; Cytoplasm divides to form two identical cells

6. Nuclear membrane disappear; Chromosomes form Chromosomes line up in the middle of the cell Chromatids split resulting in two separate identical chromosomes nuclear membrane forms around each group of chromosomes; Cytoplasm divides to form two identical cells

7. 4.3: Meiosis is necessary for sexual reproduction “Making a new ME” Diploid cell: any cell that contains the full number of chromosomes (human body cells) Gametes: cells that contain half of the usual number of chromosomes (one chromosome from each pair); haploid cells (egg cell & sperm cell) Fertilization: process that takes place when a sperm and egg cell combine to form one new cell Meiosis: a special kind of cell division that produces haploid cells Meiosis only takes place in the reproductive tissues of an organism

8. Meiosis I Before it begins, the chromosomes of the parent cell are copied (twice as many chromosomes as usual 1. Prophase 1: Duplicated chromosomes pair up and nuclear membrane disappears 2. Metaphase 1: Chromosome pairs line up in the center of the cell 3. Anaphase 1: Two copies of one homolog are pulled apart 4. Telophase 1 & Cytokinesis: a new cell membrane forms at the center of the cell and the cytoplasm is separated to form 2 daughter cells.

10. Meiosis II 1. Prophase 2: There are two copies of each chromosome attached together 2. Metaphase 2: Each duplicated chromosome lines up separately along each cell’s center 3. Anaphase 2: The two attached copies of each chromosome separate and are pulled to opposite poles on each cell 4. Telophase 2 and Cytokinesis: A new cell membrane forms splitting the cytoplasm to form four haploid cells In male organisms, these gametes become sperm In female organisms, at least one of the cells becomes an egg. The rest dissolve back into the organism.

12. Meiosis and Mitosis differ in some important ways Meiosis Haploid Cells (gametes) Two cell divisions Chromosomes are copied before the first cell division but not the second Daughter cells produced contain only half the genetic material of the parent Mitosis Diploid Cells (human body cells) One cell division Chromosomes are always copied before division Daughter cells produced contain exactly the same genetic material as the parent