L25 - Wednesday,November24,2010 CellDivision Reading:...

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Wednesday, November 24, 2010 Cell Division Reading: Chapter 18, pages 609-634  Objectives: The eukaryotic cell cycle can be divided into  interphase  and  cell division Interphase can be further divided into three phases:  o G 1  = Gap Phase #1 (after mitosis but before DNA synthesis) o S Phase  = DNA Synthesis Phase o G 2  = Gap Phase #2 (after DNA synthesis but before mitosis) Many profound changes occur during mitosis. For example, in a mitotic animal  cell:  1. The cell has become round (usually), and actin has formed a central ring  with myosin. This ring will later contract to divide the cell. 2. The centrosome has divided to form the two spindle poles, and  microtubules have reorganized to form the mitotic spindle.  3. Chromosomes have condensed, and transcription has ceased.  4. The nuclear envelope has broken down, thereby allowing microtubules  to bind to the chromosomes.  5. The Golgi apparatus has fragmented, and secretion has stopped.  Microtubule dynamic instability is accelerated during mitosis as the microtubules  reorganize to form the mitotic spindle.  The  kinetochore  is the site at which microtubules bind to the chromosome. The  kinetochore consists of proteins complexed with a DNA region called the  centromere During  metaphase , all of the chromosomes line up in the center of the cell. Two  processes then drive the separation of the chromosomes:  o Once the chromosomes have all lined up, adhesive proteins in the 
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This note was uploaded on 02/09/2011 for the course BIOS 20182 taught by Professor Lahn during the Spring '11 term at UChicago.

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L25 - Wednesday,November24,2010 CellDivision Reading:...

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