Mitosis and Meiosis Mitosis and Cytokinesis Biology Fall 2012 Objectives Summarize the events of the four stages of mitosis Differentiate cytokinesis in animal and plant cells Bell Ringer 1. What do you think the following prefixes mean? A. Pro- B. Meta- C. Ana- D. Telo- 2. How does a cells ATP use change during mitosis? Bell Ringer 1. What do you think the following prefixes mean? A. Pro- earlier than B. Meta- later than, or after C. Ana- up or back D. Telo- end 2. How does a cells ATP use change during mitosis? 1. The events of mitosis require a lot of additional energy, which is supplied by ATP Chromatid separation in Mitosis Last two phases of the cell cycle: Mitosis and cytokinesis Chromatid separation in Mitosis Mitosis: nucleus divides to form two nuclei each containing a complete set of the cells chromosomes Cytokinesis: cytoplasm is divided between the two resulting cells Chromatid separation in Mitosis During mitosis chromatids are physically moved to opposite sides of dividing cell with help of spindle Spindle: cell structures made up of both centrioles and individual microtubule fibers that are involved in moving chromosomes during cell division Forming the Spindle Centrosome: organelle that organizes the assembly of the spindle At each of cells poles In animal cells a pair of centrioles are found in each centrosome Forming the Spindle Centrioles and spindle fibers are made of hollow tubes of protein Called microtubules Spindle fibers made of individual microtubules Centrioles made of 9 triplets of microtubules arranged in a circle Forming the Spindle Plant cells DO NOT have centrioles Form a spindle that is almost identical to that of an animal cell Separation of Chomatids by Attaching Spindle Fibers Two sets of microtubules extend out toward opposite poles Once microtubules attach to the centromeres and poles, the two chromatids in each chromosome can be separated Separation of Chomatids by Attaching Spindle Fibers Paired chromosomes separate One of the pair of chromatids will move to one of the poles of the cell The second member will move to the other pole Chromatids draw closer to the poles of the cell as these microtubules are broken down bit by bit and become shorter Mitosis Step #1: Prophase Chromosomes coil up and become visible Nuclear envelope dissolves and a spindle forms Mitosis Step #2: Metaphase Chromosomes move to the center of the cell Line up along equator Spindle fibers link chromatids of each chromosome to opposite poles Meta = middle Mitosis Step #3: Anaphase Centromeres divide Two chromatids (now called chromosomes) move toward opposite poles as the spindle fibers attached to them shorten Mitosis Step #4: Telophase Nuclear envelope forms around the chromosomes at each pole Chromosomes now at opposite poles uncoil and spindle dissolves Mitosis complete! Cytokinesis Cytoplasm of cell is divided in half Cell membrane grows to enclose each cell, forming two separate cells Cytokinesis In animal cells: Lack cell walls Cell is pinched in half Cytokinesis In plant cells: Have cell walls Form a cell plate Cell plate: membrane bound cell wall that forms across the middle of the plant cell New cell wall then forms on both sides of cell plate, separates the plant cell into two new cells Cytokinesis Animal Cell Plant Cell Review White boards: Draw prophase Draw metaphase Draw anaphase Draw telophase Draw cytokinesis in plant cells Draw cytokinesis in animal cells