Cell Division:

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Cell Division Mitosis
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Important Vocabulary Words

• Eukaryotic cells - cells with a nucleus
• Prokaroytic cell - cells without a nucleus
• Cytokinesis - division of the cytoplasm
• Somatic cells - body cells ( humans have 46
  chromosomes in every normal somatic cells)

• Interphase - non reproducing stage in which a
  cell spents most of its life
• Cell Cycle - cycle of cell growth and division
  involving interphase and mitosis
• Mitosis - division of the nucleus

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How do Cells Divide?
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A. Two kinds of cell division mitosis and
meiosis
1. Mitosis
a. Results in new cells with genetic material
that is identical to the original cell.
b. Occurs in the reproduction of unicellular
organisms
c. Also creates additional tissue or organ cells
in multicellular organisms
2. Meiosis
a. Reduces the chromosome number by half in new
cells
b. New cells join together later in the
organism's life cycle to produce cells with a
complete set of chromosomes
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Why do cells need to divide?
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A. Increase the number of cells for growth
B. Replace worn out or damaged cells
C. Reproduction of organism
D. Control volume to surface ratio
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The Key to Cell Division
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A. Chromosomes carriers of the genetic material
that is copied and passed from generation to
generation
1. Made up of DNA and protein
2. Cells of every org have a specific number of
chromosomes
3. Not visible in cells except during cell
division
4. Spend most of their time as Chromatin
a. Long strands of DNA that are wrapped around
proteins and appear hazy and unorganized
through the microscope this loose arrangement
is necessary for copying to occur.
i. this loose arrangement is necessary for
copying to occur.
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b. When get ready to divide, the chromatin
coils and condenses into what we call
Chromosomes.
c. When visible, consist of two identical siste
chromatids that are joined in the center at
the centromere
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What is the Eukaryotic Cell Cycle?
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Mitosis
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A. The sequence of growth and division of a cell.
1. During this time, a cells grows, prepares for
division, and divides to form two daughter
cells.
2. The cell cycle consists of 4 phases
a. G1 phase, S phase, G2 phase, M phase
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B. Interphase G1, S, and G2
1. Interphase is very long (cells spend most of
time here)
2. G1 phase cell growth cells increase in
size and synthesize new proteins and organelles
3. S phase chromosomes are replicated and the
synthesis of DNA molecules takes place key
proteins associated with the chromosomes are
synthesized during this time
4. G2 phase shortest of 3 phases many of the
organelles and molecules required for cell
division are produced
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Interphase
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C. Mitosis M phase
1. Occurs during cell division
a. Includes heart cells, liver cells, skin
cells, etc. NOT sperm and egg
2. Cells divide once into 2 cells (daughter
cells)
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Chromatin condenses into chromosomes
Homologous pairs of chromosomes separate into
chromatids
2 identical daughter cells form when sister
chromatids separate
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3. A continuous process that is divided into 4
phases prophase, metaphase, anaphase,
telophase (PMAT)
a. Prophase
i. the nucleus of the cell organizes the
chromatin into chromosomes
ii. centrioles separate and take up positions on
opposite sides of the nucleus
iii.nucleolus disappears, nuclear membrane
breaks down

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Mitosis
Prophase
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b. Metaphase - spindles form
i. chromosomes attached at the center (or
centromeres) line up on the spindle at the
center of the cell
ii. Chromosomes line up in center of cell along
equator plane is called the metaphase plate
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Mitosis
Metaphase
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c. Anaphase
i. Chromosomes separate at the center
ii. spindles pull them toward either end of the
cell
iii.nuclear membrane forms around the
chromosomes as they disorganize
NOW EACH CHROMATID IS A SEPARATE CHROMOSOME !
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Mitosis
Anaphase
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d. Telophase
i. Cell membrane grows across the center between
the two nuclei
ii. The chromosomes return to a less tightly
coiled chromatin state
iii. Two new daughter nucleuss have visible
nucleoluss
MITOSIS IS NOW COMPLETE, BUT NOT CELL DIVISION !
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Mitosis
Telophase
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e. Cytokinesis
i. the division of the cytoplasm with the help
of proteins under the plasma membrane
ii. usually occurs during the same time as
telophase
iii. In animal cells, the plasma membrane
pinches in along the equator of the cell
-draw-string effect forms from the
outside-in, called a cleavage furrow
iv. In plant cells, the cell plate forms from
inside out NO CLEAVAGE FURROW
-instead, vesicles from Golgi apparatus move
along microtubules to the middle of the cell
where they coalesce, producing the CELL PLATE
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Regulating the Cell Cycle
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A. Timing and rate of cell division in an
organism are crucial to normal growth,
development and maintenance
1. 2 big categories of control
a. Molecular control system drives the cell cycle
b. Internal and external cues help regulate the
cell cycle
i. When cells come into contact with other
cells, they stop growing
2. Uncontrolled Cell Growth
a. If growth is not controlled, then crowding
and even tissue damage may result
b. Ex. Cancer disorder where bodys own cells
lose the ability to control growth can crowd
and even damage tissue in surrounding area
forms tumor
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i. Benign vs. malignant tumors benign are
localized and not spreading malignant tumors
become invasive enough to impair normal
function of other organs
ii. Also, malignancies are capable of breaking
off and starting up in another location --
metastasis
Breast Cancer Cell