Three reasons why cells reproduce by asexual reproduction: 1. Growth 2 Three reasons why cells reproduce by asexual reproduction: 1. Growth 2. Repair 3. Replacement 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.

Animated Mitosis Cycle http://www.cellsalive.com/mitosis.htm Interphase Prophase Metaphase Anaphase Telophase & Cytokinesis

Interphase occurs before mitosis begins Cell is doing all other activities (growth, specilalized functions) Chromosomes (we have 46 of them) appear as threadlike coils (chromatin) at the start, the chromatin is copied (duplicated – so there are 92) to prepare for cell division Other organelles are also copied Centrioles are copied Centrioles CELL MEMBRANE Nucleus Cytoplasm

Interphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Prophase Chromatin thickens/condenses into chromosomes Each chromosome (because it was copied already) consists of 2 identical stands called sister chromatid These are held together by a centrometre The nuclear membrane dissolves Centrioles (or poles) begin to move to opposite end of the cell. Spindle fibers form between the poles. Centrioles Sister chromatids Spindle fibers

Prophase Plant Cell Animal Cell Spindle fibers Centrioles Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Metaphase Chromatids (or pairs of chromosomes) attach to the spindle fibers. Chromosomes line up in the middle plane of the cell Centrioles Spindle fibers

Metaphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Anaphase Chromatids (or pairs of chromosomes) separate and begin to move to opposite ends of the cell by being pulled by the spindle fibers contracting to the centrioles The split sister chromatids are called daughter chromosomes Centrioles Spindle fibers

Anaphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Telophase Two new nuclei (nuclear membranes) form around the daughter chromosomes. Chromosomes appear as chromatin (threads rather than rods). Mitosis ends. Nuclei Nuclei Chromatin

Telophase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Cytokinesis occurs after mitosis Cell membrane moves inward (is pinched) to create two daughter cells – each with its own nucleus with identical chromosomes in an animal cell In a plant cell, a new cell wall forms and divides into two daughter cells.

Animal Mitosis -- Review Interphase                                                              Prophase                                                              Metaphase                                                              Anaphase                                                              Telophase                                                             

Plant Mitosis -- Review Interphase                                                              Prophase                                                              Metaphase                                                              Anaphase                                                              Telophase                                                             

Cell Cycle