 Negatively charged  Double stranded  Wraps around histones  CHROMOSOME=chromatid + kinetochore  46 chromosomes in humans

 Cell cannot survive unless there is enough DNA to support the protein needs of the cell  Some really large cells are multi- nucleated › More nuclei = › more DNA = › quick protein making

Cell Reproduction Cell Division= making 2 daughter cells from one parent cell AKA : Asexual Reproduction Happens in all cells New cells are genetically identical!

 Bacteria  Circular DNA  Produce 2 daughter cells by BINARY FISSION  DNA copied  Know steps!

How do little elephants grow up to be BIG elephants?

Only happens in eukaryotes. Only happens in somatic cells. Cells reproduce constantly. The process of mitosis begins after a sperm fertilizes an egg.

Skin cancer - the abnormal growth of skin cells - most often develops on skin exposed to the sun.

Animated Mitosis Cycle 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 CELL MEMBRANE Nucleus Cytoplasm

Animal Cell Plant Cell Photographs from:

Mitosis begins (cell begins to divide) Centrioles appear and begin to move to opposite end of the cell. Spindle fibers form between the poles. Nuclear membrane breaks down. Centrioles Sister chromatids Spindle fibers

Animal Cell Plant Cell Photographs from: Spindle fibers Centrioles

Meta = Middle Centromere/Kinetochore replicate Sister Chromatids (or pairs of chromosomes) attach to the spindle fibers. Chromosomes line up along the equator Centrioles Spindle fibers

Animal Cell Plant Cell Photographs from:

Chromatids (or pairs of chromosomes) separate and are pulled to the poles Pulled by spindle fibers. Centrioles Spindle fibers

Animal Cell Plant Cell Photographs from:

Two new nuclei form. Nuclear Membrane reforms Spindle Fibers fall apart Chromosomes uncoil into chromatin (thread) Cleavage : membrane pinches to make 2 identical cells (Cytokinesis) Nuclei Chromatin

Animal Cell Plant Cell Photographs from:

Cell membrane moves inward to create two daughter cells – each with its own nucleus with identical chromosomes.

Plant Mitosis -- Review Interphase Prophase Metaphase Anaphase Telophase Cytokinesis

Animal Mitosis -- Review Interphase Prophase Metaphase Anaphase Telophase Cytokinesis

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25 - Cell Division 25

Why is mitosis important? Growth and replacement of dead, lost, or damaged cells Ensures each daughter cell gets a complete and exact copy of the genetic material from the parent cell in the quickest, most efficient way

28 Means division of the cytoplasm Means division of the cytoplasm Division of cell into two, identical halves called daughter cells Division of cell into two, identical halves called daughter cells In plant cells, cell plate forms at the equator to divide cell In plant cells, cell plate forms at the equator to divide cell In animal cells, cleavage furrow forms to split cell In animal cells, cleavage furrow forms to split cell copyright cmassengale

29 Cleavage furrow in animal cell Cell plate in plant cell copyright cmassengale

30 Parent Cell Two identical daughter cells copyright cmassengale

31 If mitosis is not controlled, unlimited cell division occurs causing cancerous tumors If mitosis is not controlled, unlimited cell division occurs causing cancerous tumors Oncogenes are special proteins increase the chance that a normal cell develops into a tumor cell Oncogenes are special proteins that increase the chance that a normal cell develops into a tumor cell Cancer cells copyright cmassengale