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Slide 2 Phases of Cell Division Interphase (stage between cell division) Interphase (stage between cell division) Prophase Prophase Metaphase Metaphase Anaphase Anaphase Telophase Telophase By: Ms. Reis By: Ms. Reis Slide 3 Review Each body cell has 2 sets of 23 chromosomes Each body cell has 2 sets of 23 chromosomes Therefore a normal human cell has 46 chromosomes Therefore a normal human cell has 46 chromosomes Slide 4 Cell Division Cells divide for several reasons: To repair and heal tissues To repair and heal tissues To exchange materials efficiently with their environment. Food comes in and wastes go out. To exchange materials efficiently with their environment. Food comes in and wastes go out. To send messages to the nucleus efficiently. To send messages to the nucleus efficiently. Slide 5 Mitosis Mitosis is a process of cell division producing two daughter cells from a single parent cell. Mitosis is a process of cell division producing two daughter cells from a single parent cell. The daughter cells are identical to one another and to the original parent cell. The daughter cells are identical to one another and to the original parent cell. Note: Parent cell - the cell that divides Note: Parent cell - the cell that divides Daughter cell the cells that result from cell division Daughter cell the cells that result from cell division Slide 6 Down Syndrome Slide 7 Karyotype A photograph showing the number, shapes and sizes of chromosomes in a cell. A photograph showing the number, shapes and sizes of chromosomes in a cell. All pairs of chromosomes are homologus (identical in size and shape) except the sex chromosomes (23rd pair) All pairs of chromosomes are homologus (identical in size and shape) except the sex chromosomes (23rd pair) One chromosome comes from the father (paternal) one chromosome comes from the mother (maternal One chromosome comes from the father (paternal) one chromosome comes from the mother (maternal Slide 8 Slide 9 The Cell Cycle Slide 10 Interphase The cell prepares for mitosis by growing rapidly The cell prepares for mitosis by growing rapidly Chromosomes duplicate in the nucleus Chromosomes duplicate in the nucleus Longest stage of the cell cycle Longest stage of the cell cycle Slide 11 Chromatin DNA molecules & proteins in a tangled fibrous mass during interphase. Chromatin is composed of 60% protein, 35 % DNA, and 5 % RNA. DNA molecules & proteins in a tangled fibrous mass during interphase. Chromatin is composed of 60% protein, 35 % DNA, and 5 % RNA. Slide 12 Centromeres The original chromosome and its duplicate are attached at the centromere. The original chromosome and its duplicate are attached at the centromere. Sister chromatids the original chromosome and its duplicate while attached at the centromere. Sister chromatids the original chromosome and its duplicate while attached at the centromere. Slide 13 Prophase Chromosomes shorten and thicken Chromosomes shorten and thicken Nuclear membrane dissolves Nuclear membrane dissolves Centrioles move to opposite poles of cell in animal cells Centrioles move to opposite poles of cell in animal cells Formation of spindle fibers Formation of spindle fibers Slide 14 Metaphase 46 sister chromatids line up at the equatorial plate. 46 sister chromatids line up at the equatorial plate. Slide 15 Anaphase Spindle fibers pull sister chromatids (duplicated chromosomes) apart to the opposite end of the cell. Spindle fibers pull sister chromatids (duplicated chromosomes) apart to the opposite end of the cell. Centromeres divide. Centromeres divide. Slide 16 Telophase Cell begins to pinch in two Cell begins to pinch in two New nuclear membrane starts to form New nuclear membrane starts to form Cytokinesis - division of the cytoplasm and organelles between both daughter cells Cytokinesis - division of the cytoplasm and organelles between both daughter cells Slide 17 Conclusion Each new cell ends up with the same amount of genetic material as the original cell. Each new cell ends up with the same amount of genetic material as the original cell. Both daughter cells are identical to the parent cells. Both daughter cells are identical to the parent cells. Slide 18 Cytokinesis In animal cells the cell membrane pinches inward at the equator of the cell, producing a furrow. In animal cells the cell membrane pinches inward at the equator of the cell, producing a furrow. In plant cells a cell plate is formed across the equator of the cell. Cellulose is added to the cell plate to form a new cell wall. In plant cells a cell plate is formed across the equator of the cell. Cellulose is added to the cell plate to form a new cell wall. Slide 19 Discussion Question How many chromosomes would you expect to find in each daughter cell after mitosis? How many chromosomes would you expect to find in each daughter cell after mitosis? Predict what might happen to each daughter cell if all the chromosomes moved to only one side of the cell during anaphase. Predict what might happen to each daughter cell if all the chromosomes moved to only one side of the cell during anaphase. Why is it necessary to duplicate the nuclear material? Why is it necessary to duplicate the nuclear material?