two types mitosis used for growth, repair, and asexual reproduction results in 2 exact copies of...
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Mitosis Starts with 1 cell, results in 2 cells that are exact copies of the original. Four phases: Prophase Metaphase Anaphase TelophaseTRANSCRIPT
CELL DIVISION
Two Types
Mitosis Used for growth, repair, and asexual
reproduction Results in 2 exact copies of the original
cell Meiosis (next chapter)
Used in sexual reproduction Results in cells with ½ the number of
chromosomes of the original cells More on this later.
Mitosis
Starts with 1 cell, results in 2 cells that are exact copies of the original.
Four phases: Prophase Metaphase Anaphase Telophase
Prophase Chromatin coils to
form chromosomes Nucleolus and
Nuclear membrane breaks down
Centrioles move away from each other toward the poles (animals only).
Spindle fibers form
Metaphase
Chromosomes are moved to the equator by spindle fibers.
Anaphase
Sister chromatids separate.
Separated chromatids (now called daughter chromosomes) move toward the poles.
Telophase
Spindle fibers break down.
Chromosomes unwind to form of chromatin.
Nuclear membrane and nucleolus reform.
Which phase?
Metaphase
Which phase?
Telophase
Which phase?
Anaphase
Which phase?
Prophase
Animations
http://www.cellsalive.com/mitosis.htm
Cytokinesis
The physical division of the cytoplasm.
Animals pinch their cell membrane inward until 2 cells are formed.
Plants form a “cell plate” to form a new cell.
Control of the cell cycle
Control of the Cell Cycle
Not all cells follow the cell cycle at the same rate.
Skin cells Liver cells Nerve cells
Control of the Cell Cycle
Normal cells: Divide until they come in contact with
one another, then stop when they become too crowded.
Only grow when connected to something.
Respond to internal and external signals Many molecules control the cell cycle from
inside the cell and from outside the cell. “Cyclins” and Growth Factors are two
examples of these molecules (they act like stop and go signals).
Control of the Cell Cycle
Cancer Cells: Have lost control of the cell cycle. Do not respond the system of chemical
signals Do not stop dividing when in contact
with other cells. Can move from one place in the body to
another. Interrupts normal tissue activity.
Cancer Terms
Tumor – a mass or lump of cells resulting from uncontrolled cell division. Benign tumor – tumor that does not
spread to other areas. Malignant tumor – invades surrounding
tissues Apoptosis – programmed cell death
(normal) Cancer cells do not respond to this.
Causes of cancer
Caused by anything that changes the DNA responsible for controlling the cell cycle. Tobacco Radiation Sunlight Viral infections Random mutation
Treatments
Remove tumor by surgery if possible. Radiation treatment Chemotherapy
Cell Differentiation Zygote – a
fertilized egg
Differentiation – process in which cells become specialized.
Stem cells
Undifferentiated cells The zygote and the first few cells
that arise from it can become any type of cell. Totipotent cell – a cell that can become
any type of cell The zygote develops into a
blastocyst. Pluripotent cell – a cell that can become
most, but not all types of cells.Undifferentiated cells
Stem Cells continued
Embryonic stem cells are the cells found in the early embryo Are pluripotent
Stem cells continued Adult stem cells are
cells that replace certain types of cells in our bodies when needed. Multipotent cell – has
a limited potential to develop into many types of cells
Ex. Adult stem cells in the bone marrow can develop into any type of blood cell (red, white, or platelets.
Stem cells continued
Benefits of stem cell research? Ethical issues?