Cell Processes: Mitosis and Meiosis – Teacher’s Guide
Kit # 3674-07
Background OBJEcTIVES ‹ Make predictions about natural phenomena occurring during the cell cycle, ‹ Describe the events that occur in the cell cycle. ‹ Construct an explanation, using visual representations or narratives, as to how DNA in chromosomes is transmitted to the next generation via mitosis, or meiosis followed by fertilization. ‹ Represent the connection between meiosis and increased genetic diversity necessary for evolution. ‹ Evaluate evidence provided by data sets to support the claim that heritable information is passed from one generation to another generation through mitosis, or meiosis followed by fertilization. ‹ Construct a representation that connects the process of meiosis to the passage of traits from parent to offspring. ‹ Construct an explanation of the multiple processes that increase variation within a population..
Reproduction in living things can be achieved through either asexual or sexual processes. In asexual reproduction, offspring organisms are genetically similar to the parent organism with limited, if any, introduction of DNA from another individual. In sexual reproduction, offspring organisms are generated by combining one half of the DNA from each of two parent individuals to produce a diploid (2N) offspring that has two complete sets of chromosomes and genes. The process of sexual reproduction enables greater genetic variation in offspring than asexual reproduction. Multicellular, diploid, eukaryotic organisms use both types of cellular reproduction. Growth and development of the organism occurs through asexual reproduction of cells through the process of mitosis where every normal daughter cell is diploid, carrying two copies of each chromosome and set of genes. In mitotic reproduction, these daughter cells are genetic replicates of both the parent cell and the sister cell. Most single cell eukaryotes reproduce by simple mitosis, producing more replicates of the parent organism. Mitosis The mitotic cell cycle is a highly regulated process that insures accuracy in DNA replication and equal division into daughter cells. Defects in accurate reproduction will cause abnormalities that will result in decreased viability of both the daughter cells and the multicellular organism through a variety of mechanisms (including apoptosis and cancer). Mitosis is a continuous process that can be described by a sequence of stages. The stages are defined by molecular and cytosolic events. Visual inspection of dividing cells through the microscope has defined three main stages (Figure 1) that can be further subdivided (Figures 2, 3 on the next pages): ‹ please check figure #’s - these were renumbered, for better clarity Mitosis: The cells are separating DNA equally for two future daughter cells. Cytokinesis: The daughter cells are separated into two individual cells,
Figure 1
Interphase: The cells look quiescent, (continued on next page)
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