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genetics-lab - Genetics page 1 of 8 ANAT 11110 Fall 2011...

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Genetics page 1 of 8 ANAT 11110 Lab 3 Fall 2011 Genetics Cell Division and Inheritance The process of growth and development in multicelled organisms is due, for the most part, to the process of cell division. This allows the human body to go from a single fertilized cell to a mature body of approximately 75 trillion cells. Repair and replacement of damaged or aged tissue also takes place mostly through the process of cell division. It is important, therefore, to understand how the process of cell division (i.e., mitosis) takes place. When it comes time for the organism to reproduce itself as a whole entity, the process is somewhat different and is called meiosis. Here the goal is not to produce an exact duplicate of the original organism, but to pass just one copy of the genetic material on into the next generation. In this lab, we will study the processes of mitosis and meiosis and begin to acquire some of the language of genetics and heredity. Station 1: Mitosis The cells of the body are of one of two types. Most of the cells in the body are somatic cells. The only cells which are not somatic cells are those involved in the production of sex cells (aka, gametes). When somatic cells reproduce, it is necessary for them to produce an exact duplicate of the original cell. The life of the somatic cell is divided up into several phases. The vast majority of the cell's life is spent in interphase . This is the phase in which the cell carries out its primary functions, e.g., as an epithelial cell in the skin, or a smooth muscle fiber in the stomach. Interphase can be further subdivided. The G 0 phase is where the cell carries out its specialized function. In the G 1 phase , the cell is preparing for cell division; manufacture of organelles outside the nucleus is increased to provide enough for two cells. The G 1 phase is followed by the S phase , where the chromosomes within the nucleus are duplicated, preparatory to cell division. Lastly, the G 2 phase finishes up the preparations for cell division, being devoted to last-minute protein synthesis and the completion of centriole replication. The process of mitosis is also broken down into several phases, beginning with prophase . During prophase, the duplicated chromosomes condense out of the chromatin, becoming visible under the light microscope. As the result of chromosome duplication in the S phase, there are now two copies of each chromosome, held together by a centromere ; each copy is referred to as a chromatid , until it is separated from its duplicate later in the process. The two pairs of centrioles, produced at the end of the G 2
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Genetics page 2 of 8 phase, split up, with each pair migrating to opposite poles of the cell, with spindle fibers extending between them. Prophase ends with the nuclear membrane disappearing and the chromosomes becoming attached to the spindle fibers, via the centromere.
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