Cell Division Are you two twins Asexual Reproduction

Cell Division

Are you two twins? • Asexual Reproduction: – Used by many unicellular organisms, plants, and lower animals. – Involves only mitotic cell division = each offspring has exactly the same heredity as its parent. – Usually rapid compared to sexual reproduction.

Phases of the Cell Cycle • The cell cycle consists of – Interphase (cell growth and copying of chromosomes in preparation for cell division) – Mitotic (M) phase (mitosis and cytokinesis) • Interphase (about 90% of the cell cycle) can be divided into subphases: – G 1 phase (“first gap”) – cell growth & normal functions – S phase (“synthesis”) – DNA copies – G 2 phase (“second gap”) – mitosis

Animated Cycle http: //www. cellsalive. com/cell_cycle. htm

Mitosis • Cells divide to form 2 identical “daughter cells” • Occurs in stages – I PMAT C

Interphase The cell prepares for division – DNA replicated – Organelles replicated – Cell increases in size

Interphase Animal Cell Plant Cell Photographs from: http: //www. bioweb. uncc. edu/biol 1110/Stages. htm

Mitosis Stage 1 - Prophase • DNA coils into chromosomes • Centrioles move to opposite sides of cell • Nuclear membrane dissolves • Spindle fibers form between the centrioles as they move apart

Prophase Animal Cell Plant Cell Photographs from: http: //www. bioweb. uncc. edu/biol 1110/Stages. htm

Mitosis Stage 2 - Metaphase • Chromosomes attach to spindle fibers and line up in the middle

Metaphase Animal Cell Plant Cell Photographs from: http: //www. bioweb. uncc. edu/biol 1110/Stages. htm

Mitosis Stage 3 - Anaphase • Chromosomes separate • Spindle fibers retract, pulling the chromosome pairs apart

Anaphase Animal Cell Plant Cell Photographs from: http: //www. bioweb. uncc. edu/biol 1110/Stages. htm

Mitosis Stage 4 - Telophase • New nuclear membrane forms around chromosomes – Cell membrane pinches in to form the 2 new daughter cells

Telophase Animal Cell Plant Cell Photographs from: http: //www. bioweb. uncc. edu/biol 1110/Stages. htm

Mitosis Stage 5 - Cytokinesis • Division of cytoplasm & organelles • Begins in anaphase • “Pinches off” between new nuclei to form 2 individual cells

Mitosis • Cell division regulated by cell type (depends on gene activation) • Uncontrolled cell division = cancer

Mitosis Animation http: //www. cellsalive. com/mitosis. htm