Chapter 10 Cell Cycle Notes
The cell theory states that all cells come from other living cells. Cells divide and create
more cells for many reasons:
1. Cells divide for the survival of the individual organism Cell division is used for
growth, development, maintenance, and repair of the organism. This is carried out by:

Mitosis- division of body cells to make more of the same kind of cell. The parent
cell is the original cell inside the organism.
The daughter cells are the two identical cells created when the parent cell divides.
2. Cells divide for the survival of the species  to reproduce and create more organisms
that have genetic make-up similar to the parents:

Sexual reproduction - two separate organisms produce egg and sperm that must
combine or fuse together to produce offspring.
Meiosis process of making egg cells and sperm cells.
Fertilization
 the fusion of egg and sperm to produce a new organism.

Asexual reproduction- offspring are produced by only an individual organism.
Spores are produced by mold and other fungi & grow into more fungi.
Binary fission is the process of a bacterium splitting in two new bacteria.
THE CELL CYCLE: The life cycle of a cell – from birth to life and finally division of the cell.
Cell Cycle- is defined as the life of a cell from the beginning of one Interphase to the
_beginning of the next Interphase . (with cell division in between)
The steps of the Cell’s life cycle:
Step (1.) Interphase  Three parts of Interphase: G1, S, and G2 (in this order)
Step (2.) Cell Division  Two parts of Cell Division: Mitosis and Cytokinesis
(in this order)
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Step 1:
Interphase – is the growth and development phase of the cell cycle. Three parts:
(1.) Growth One (G1) phase ( 2.) Synthesis (S) phase (3.) Growth 2 (G2) phase
1. The G1 phase is the initial growth phase of
the cell. The cell grows and carries out its
routine functions. This is the longest phase
of interphase. Many cells stop growing and
get stuck in this phase for the entire life of the
organism (Ex. nerve cells). Other cells get
stuck in G1 of interphase until cell
division is needed for growth or repair.
G1
G2
S
2. The S phase is when DNA replication
occurs. After DNA replication the cell
has two complete copies of its DNA. At
this point, the cell is committed to
dividing.
3. In the G2 phase, the cell continues to grow
and the final preparations for cell division
are made.
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Step 2: Cell Division: - the creation of two daughter cells from one parent cell. *Each
daughter cell will have the same number of chromosomes as the parent cell.*
Two Parts of Cell division: Mitosis and Cytokinesis
1. Mitosis – “division of the nucleus”. It is a
2. Cytokinesis “division of the cell cytoplasm”. It
synchronized set of events that will
is the physical separation of the cytoplasm into
separate chromosomes, so that the two
two new daughter cells. It is the end of cell
nuclei formed will be identical. It is the
beginning of cellular division.
(ProphaseMetaphaseAnaphaseTelophase)
division. New cells pinch off from each other in
animal cells. In plants, a cell plate is formed,
because plants also have cell walls.
1. Chromosome: coiled DNA structures within the nucleus containing genetic information that is
passed on from generation to generation
2. Sister chromatid: one of two identical “sister” parts of a duplicated chromosome-formed
during S phase
3. Centromere: chromosome region that joins 2 sister chromatids
Step #1: Prophase
1.DNA coils & becomes chromosomes
2. Centrioles move to opposite ends of cell
3. Spinde fibers attach to chromosomes
4. Nuclear membrane breaks down
Step #2: Metaphase
1. Spindle fibers push & pull chromosomes until they
line up across center of cell
2. Centromere of each chromosome pair is attached
to a spindle fiber
Step # 3: Anaphase
1. Spindle fibers shorten & paired chromatids
separate
2. Spindle fibers pull separated chromosomes to
opposite ends of the cell
3. Centromere of each pair divides; now have
individual chromosomes
Step #4: Telophase
1. Chromosomes begin to uncoil and
decondense
2. Nuclear membrane reforms around each new set
of chromosomes
Step #5: Cytokinesis
1. Cytokinesis is division of the cytoplasm
2. Distributes the organelles
a. In animal cells, the cell membrane
pinches in two.
b. In plant cells, a cell plate forms across
the middle.
CANCER is the caused by uncontrolled cellular division. Most cells don’t divide except for
repair or maintenance. Cancerous cells keep dividing; they crowd out and steal
nutrients from healthy tissue. Cancer “kills” when a mass of cancer cells called a
tumor interferes with the functions of major organs.