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How do little elephants grow up to be BIG elephants? Cell Growth › › Since living things grow by producing more cells, the cells of an adult animal are no larger than those of young animals---there are just more of them. Limits to Cell Growth (read page 241) 1. DNA overload 2. Exchanging Materials The process of asexual reproduction begins after a sperm fertilizes an egg. Skin cancer - the abnormal growth of skin cells - most often develops on skin exposed to the sun. Cell that reproduce by asexual reproduction reproduce constantly. The Cell Cycle The Cell Cycle@ the cell cycle is a sequence of growth and division there are 4 phases (Fig 10-4) G1 = cell growth S = DNA synthesis G2 = prepare for cell division M = cell division; Mitosis and Cytokinesis Cell Cycle Regulation Cyclins regulate the cell cycle Ex protein called p53 Cancer is the unregulated growth of cells. These cells do not respond to cyclins. - Cancerous cells divide uncontrollably to form masses of cells called tumors. Animated Mitosis Cycle http://www.cellsalive.com/mitosis.htm • Interphase • Prophase • Metaphase • Anaphase • Telophase & Cytokinesis Chromosomes are copied (# doubles) • Chromosomes appear as threadlike coils (chromatin) at the start, but each chromosome and its copy(sister chromosome) change to sister chromatids at end of this phase • Nucleus CELL MEMBRANE Cytoplasm Animal Cell Plant Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm Interphase (Growth Period) - cells spend most time in this phase - divided into 3 phases G1, S, G2 Cell grows in size Chromosomes replicate also known as DNA synthesis Cell repairs itself before division Mitosis (Division Period; PMAT@ $) - nucleus and cytoplasm divides to form 2 daughter cells - occurs in all body cells (all cells except sex which are gametes) - Each new cell has the same number of chromosomes as “parent” cell. This is called diploid (2N) number of chromosomes Example • • • Mitosis begins (cell begins to divide) Centrioles (or poles) appear and begin to move to opposite end of the cell. Spindle fibers form between the poles. Centrioles Sister chromatids Spindle fibers Prophase (Prepare) Chromosomes thicken and become visible › › chromosomes are 2 sister chromatids connected by centromere Fig 10-3 page 244 Example: › › › The nucleus, nuclear envelope and nucleolus disappear. Centrioles migrate to opposite ends of the cell in animal cells Spindle fibers form Animal Cell Plant Cell Spindle fibers Centrioles Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm • Chromatids (or pairs of chromosomes) attach to the spindle fibers. Centrioles Spindle fibers Animal Cell Plant Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm • Chromatids (or pairs of chromosomes) separate and begin to move to opposite ends of the cell. Centrioles Spindle fibers Animal Cell Plant Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm • • • Two new nuclei form. Chromosomes appear as chromatin (threads rather than rods). Mitosis ends. Nuclei Chromatin Nuclei Telophase (The cell begins to split into two; looks like telephone) › › › › chromosomes unwind spindle breaks down nucleolus and nuclear envelope reappears plasma membrane separates the 2 new nuclei - the animal cell plasma membrane pinches in Fig 10-5 Telophase - the plant cell forms a cell plate across the equator Fig 10-6 pg 248 Animal Cell Plant Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm • Cell membrane moves inward to create two daughter cells – each with its own nucleus with identical chromosomes. Cytokinesis - Although mitosis is division of the nucleus, cytokinesis is division of the cytoplasm - 2 new cells are formed that are identical to the parent cell - this process is asexual reproduction Remember Events of the Cell Cycle by IPMAT I = Interphase P = Prophase M = Metaphase A = Anaphase T = Telophase Animal vs Plant Cell Division Animal Use centriole Cell pinching Plant No centriole Cell Plate Animal Mitosis -- Review Interphase Prophase Metaphase Anaphase Telophase Interphase Plant Mitosis -- Review Interphase Prophase Metaphase Anaphase Telophase Interphase 30 - Cell Division 31 31 http://www.cellsalive.com/mitosis.htm