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Chromosomes and Cell Division
DNADNA Negatively charged
Double stranded
Wraps around histones
CHROMOSOME=chromatid + kinetochore
46 chromosomes in humans
DNA Limits Cell Size
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!
Prokaryote Cell Division
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 Cyclehttp://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
CELL MEMBRANENucleus
Cytoplasm
Animal Cell Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
• 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.
CentriolesSister chromatids
Spindle fibers
Animal Cell Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
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: http://www.bioweb.uncc.edu/biol1110/Stages.htm
• 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: http://www.bioweb.uncc.edu/biol1110/Stages.htm
• 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)
NucleiNuclei
Chromatin
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.
Plant Mitosis -- ReviewInterphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
Animal Mitosis -- Review
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
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- Cell Division
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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
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Means division of the Means division of the cytoplasmcytoplasm
Division of cell into two, Division of cell into two, identical halves called identical halves called daughter cellsdaughter cells
In plant cells, cell plate forms In plant cells, cell plate forms at the equator to divide cellat the equator to divide cell
In animal cells, cleavage In animal cells, cleavage furrow forms to split cellfurrow forms to split cell
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Cleavage furrow Cleavage furrow in animal cellin animal cell
Cell plate in plant Cell plate in plant cellcell
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Parent CellParent Cell
Two Two identical identical daughter daughter cellscells
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If mitosis is not If mitosis is not controlled, controlled, unlimited cell unlimited cell division occurs division occurs causing cancerous causing cancerous tumorstumors
Oncogenes are Oncogenes are special proteins special proteins that increase the increase the chance that a chance that a normal cell normal cell develops into a develops into a tumor cell tumor cell Cancer cellsCancer cells
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