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MITOSIS-CELL DIVISION
#1-WHY DO CELLS DIVIDE?
A. Diffusion limits cell size
Replace
Repair
Grow and develop
The larger a cell becomes, the more demands on its DNA
Trouble moving nutrients and wastes across the cell membrane
Organization
DNA is the cells library of information
If the cell gets too large, it will put too many demands on the cell
A cell needs to stay small to meet the “DNA” needs of the cell
B.
Surface areaThe total area of the surface of a three dimensional object
Affects the rate of food (Oxygen, Water) and wastes moving in and out
of the cell.
C. VolumeAmount of space occupied
Larger volume slows the rate of materials moving in and out
D RatioSurface area/volume
As the length of the cell increases, the volume increases faster surface
area
Larger ratio-quick movement of materials
Small ratio-slow movement of materials
Cells divide because they cannot get food to the center of their cytoplasm quickly
enough
#2-CELL DIVISION
A. 46 chromosomes which make up (23 pairs)
B. Chromosomes # stays the same
a. Before it becomes too large, a growing cell doubles its chromosomes
and organelles then divides.
b. Cell then splits, forming two daughter cells
C. Common Location for Cell Division
Intestinal Lining-every 24 hours
Skin
Sperm cells
Blood cells/bone marrow makes blood cells
Liver-sometimes
Cells that never divide
Muscle cells
Cardiac cells
Kidney
Nerve cells
Parent Cell=46 Chromosomes
Can split into two daughter cells, which are identical
When a new cell is created……it has (46) chromosomes
Cell Cycle Checkpoints
G1-The cell grows
S-Synthesis-Chromosomes are duplicated
G2-The cell grows
Check Points
G1
1) Checks for cell size
2) Checks that genetic material is healthy
G2
1) Check that DNA is duplicated
2) Cell size
3) Check that genetic material is healthy (No mutations)
M-Mitosis1) Check to make sure that the spindle fibers were attached to the chromosomes
If the cell could NOT get through a check point
1) Apoptosis-The cell dies
2) Repair
A. Interphase “Eye ball”
90% of the time
1. Gap 1-cell grows, doubles organelles
2. Synthesis- (S-phase)-duplication of the DNA in the cells chromosomes
3. GAP 2-cell grows, microtubules assembled
B. Stages of Mitosis
1. Prophase (pasta phase)
Visible chromosome
Nucleus disappears
2. Metaphase “middle”-Chromosomes line up at the equator
3. Anaphase “apart”
5
Telephase “two new cells are forming”
Cytokinesis-the cytoplasm cuts in half
Cyto-cell
Kinesis-to cut
Very last part of the cell cycle
In plants
A structure known as the cell plate forms midway between the divided nuclei
Cytokines is in Animals
Animal cells contract and pinch in ½ (half)
TERMS
Spindle-network of microtubules that move chromosomes during mitosis and meiosis
Equator: centerline of cell where chromosomes line up during metaphase
Poles: The opposite ends of the cell
Centrioles-animal cells only, move the spindle and chromosomes during division
Cleavage Furrow-The pinching in of animal cells during cytokinesis.
Cell Plate-disk in plant cells that divide the cell into daughter cells during cytokinesis.
Centromere-region where two sister chromatids are joined tightly together.
VI-Results of Mitosis
A. Production of 2 new daughter cells
B. Daughter cells are exactly the same as original parent cell
C. Mitosis is how organisms grow, develop and repair
When the cell cycle goes wrong……………………………..
-Normal cells will reproduce until they touch other cells
-When this happens, they stop growing
Uncontrolled Cell Growth
Cancer is a disorder in which some of the body’s own cells lose the ability to
control growth.
Cancer cells do not respond to the signals that regulate the growth of most
cells.
Divide uncontrollably
Form masses of cells called tumors
Metastasis-tumor cells break loose and spread in body.
Benign-Non-cancerous
Malignant-Cancerous Tumor
Causes of Cancer:
Genetics
Chemicals-Absestos, cigarettes, pesticides
Radiation
Diet
Certain viruses (HPV)
Prevention of Cancer
Genetic screening
Do not smoke,
Do not drink too much,
proper diet
prevent sunburns
Treatment for Cancer
Chemotherapy
 Radiation