Cell Growth
and Division
I.
A.
Background Info
Chromosomes
1.
2.
3.
Carry all the genetic
information (DNA) for an
organism.
Made of chromatin.
a) Chromatin is made of
DNA twisted around a
protein called histone.
Involved in cell growth
and division
B. Why Do Cells Divide?
1. Growth of an organism
2. Replace dead or damaged cells
3. Reproduction in single-celled organisms
4. Prevent “DNA overload”
C. Why don’t cells keep getting bigger and bigger as
an organism grows?
1.
2.
Cell membrane can’t handle the flow of materials
Nucleus can’t control the functions of a large cell
3.
Raw materials and waste could not get in or out of
the cell fast enough
So a cell divides into two new cells that are
identical to the original
4.
II. The Cell Cycle
A. Cell cycle is a series of events that takes place from one cell
division to the next
B. The time it takes to complete a cell cycle is different for every
type of cell
C. Consists of Interphase , Mitosis (cell division), and Cytokinesis
Cell Cycle Movie
1. Interphase
a. The cell is performing life functions, but not
actually dividing.
b. Chromosomes are not visible.
c. Consists of 3 phases:
1) G1 (1st growing phase) - cell growth; right after
cell division.
2) S (synthesis phase) - DNA replication (copying)
3) G2 (2nd growing phase) - replication of cell
organelles (to prepare for division) and
synthesis of cell division structures.
G1 phase
S phase
G2 phase
Interphase Movie
Bill Nye Mitosis Movie
III. Stages of Mitosis
A. Prophase
1. Nuclear membrane & nucleolus start to disappear
2. Spindle fibers and centrioles appear
3. Chromosomes are visible
Prophase Movie
B. Metaphase
1. Chromosomes line up at the center of the cell
(metaphase plate) by attaching themselves
to the visible spindle fibers
Metaphase Movie
C. Anaphase
1. The chromosomes are pulled (at the
centromeres) to the opposite poles of the cell.
2. Each chromosome now is a single chromatid.
3. Each side gets an exact copy of each
chromosome
Anaphase Movie
D. Telophase
1. Nuclear membrane and nucleolus reappears.
2. Chromosomes and spindle fibers start to
disappear.
3. Mitosis is complete at this point.
Telophase Movie
IV. Cytokinesis
A. Cytokinesis is the division of organelles and
cytoplasm
B. Two IDENTICAL daughter cells are formed
C. In plant cells the Golgi bodies secrete a cell plate
in the middle of the cell.
Cell Plate
Cell Division Quiz
Movie
V. Cancer
A.
B.
C.
Cancer is the result of uncontrolled cell division.
Can form masses of cells called tumors
If a cancer cell breaks loose from a tumor, it can spread
to other parts of the body (metastasize)
D. Causes:
1. Tobacco
2. Alcohol
3. Viruses (HPV)
4. Radiation (sun, radioactive materials)
VI. Stem Cells
A. Three to five days after fertilization, a human
embryo is a mass of cells called stem cells
B. Stem cells are have the ability to develop into any
type of specialized cell (differentiation)
Stem Cell Movie