Mitosis & Cytokinesis  Objective 4a: I can recognize the stages of mitosis from diagrams.  Objective 4b: I can put the stages of mitosis in the proper order.  Objective #4c: I can state what types of cells undergo mitosis, and why.  Objective #4d: I can list differences between how animal and plant cells divide.

 Discuss the answers to the following questions with the person next to you:  How is mitosis different from the phases of interphase?  What is the purpose of mitosis?  What kinds of cells undergo mitosis?  What are the phases of mitosis, and what happens in each of them?  So; what do you know?

G 2 Interphase cell—preparing for mitosis... How?

 Prophase  Chromatin condenses into chromosomes  Sets of sister chromatids  Nucleoli disappear  Mitotic spindle begins to form as centrioles move to opposite poles of the cell  Nuclear envelope begins to fragment and break down  Microtubules of spindle (spindle fibers) attach to centromeres of chromatids

1. Chromosomes condense into chromatin. 2. Nuclear envelope starts to break down. 3. The mitotic spindle starts to form. 4. The spindle fibers attach to the centromeres.

 Metaphase  Spindle fibers line sets of sister chromatids up on the cell equator (middle of cell)  Preparation for anaphase, where chromatids get pulled apart

1. Chromosomes are still sets of sister chromatids attached to spindle fibers at their centromeres. 2. Sister chromatids line up along the cell equator. 3. The centrioles move the sister chromatids to the cell equator.

 Anaphase  Sister chromatids are pulled apart at their centromeres  Each sister chromatid is now considered a chromosome  Separated chromosomes are pulled to opposite poles (ends) of the cell  By end of anaphase, each pole (ends) of cell has a complete set of chromosomes

1. Chromosomes are still sets of sister chromatids at the end of anaphase. 2. Sister chromatids are pulled apart at their centromeres during anaphase. 3. Two new nuclei are formed at the end of anaphase.

 Telophase  Two new daughter nuclei form at both poles  Nuclear envelopes reform around each set of chromosomes  Chromosomes uncondense back into chromatin  Cytokinesis usually begins during telophase or late anaphase  Cleavage furrow appears (animal cells) or cell plate appears (plants)

1. Chromatids are pulled apart by their centromeres 2. Chromatin condenses to chromosomes 3. Two new nuclei form at each pole of the cell

1. Prophase 2. Anaphase 3. Metaphase

1. Anaphase 2. Interphase 3. Prophase

1. True 2. False

 Differences in cytokinesis arise due to presence/absence of cell walls  Animal cells: Can just pinch in two by a process called cleavage  Uses a ring of contractile proteins in its cell membrane  Like the drawstring on sweatpants pulled tight enough to cut you in half  Plant cells: Must build a new cell wall between the two new nuclei  Golgi sends out vesicles that builds the cell plate

1. Animal cells pinch in two; plant cells build a cell plate between two new nuclei. 2. Plant cell cytokinesis makes 4 new cells; animal cell cytokinesis only makes 2 new cells. 3. Plant cells use chloroplasts; animal cells do not.

1. Metaphase 2. Telophase 3. Anaphase 4. Prophase

1. Prophase 2. Telophase 3. Metaphase 4. Anaphase

1. True 2. False

1. Body cells, because they need to be small and make more identical cells. 2. Sperm cells, because guys make a LOT of them. 3. Somatic cells, because the daughter cells need to be genetically different from the parent cell.

1. Cytokinesis finishes dividing the nucleus of the daughter cells. 2. Animal cells can pinch in two because they don’t have a cell wall. 3. Plant cells have to build a new cell wall between the two new nuclei to finish dividing completely.