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Cell Growth and Reproduction
Cell Theory:
– All cells come from pre-existing cells.
Body Cell Division: Mitosis
– Cells produced from one cell (parent
cell).
– Result is two or more identical cells.
– Repairs worn-out tissue. (ex: skin)
– Allows organisms to grow and change.
Ivy to wrap around a trellis
From birth to rebirth, a cell progresses through
stages that make up the Cell Cycle.
• Interphase -regular cell activities and growth
• Mitosis-cell division is just a short stage in in
a cells life.
Progress through the cell cycle is carefully regulated.
Cell Cycle
Cell Growth and Reproduction
Cell Cycle: Sequence of growth and
division of the cell.
Majority of cell’s life is spent during
INTERPHASE or the cell’s growth
period
Interphase
Cell Growth and Reproduction
INTERPHASE:
– Longest phase: Growth Phase
– Cell grows in size
– Carries on metabolism
– Chromosomes are duplicated to prepare
for division
3 Stages:
Cell Growth and Reproduction
INTERPHASE:
– 3 Stages:
Cell grows, protein production is high
Cell copies its chromosomes
Centrioles replicate and cell prepares for
division
Interphase -main part of the Cell Cycle.
Chromatin (long thin
DNA molecule) is
stored in the
nucleus and it
controls the cell
activities and its
overall design and
function.
Longest part of the
cell cycle.
DNA
Replication = copying of DNA during
Interphase –Synthesis phase.
Cell Growth and Reproduction
Chromatin: long strands of DNA
wrapped around proteins
– Chromosomes exist as chromatin for most
of cell’s lifetime
– Spaghetti noodles
Chromosomes carry genetic information
that is copied and passed on to new
cells
– Like wound spaghetti
Cell Growth and Reproduction
Chromosome
Chromatin
Cell Growth and Reproduction
Before cell division, chromosome is
in spaghetti-like CHROMATIN state
As cell division begins, chromosomes take on
a new tightly packed shape
Why do you think this is important?
Cell Growth and Reproduction
After INTERPHASE, cell enters period
of division, also called MITOSIS
Mitosis: period of cell division
– As cell gets to the maximum size, it begins
to undergo MITOSIS (cell division)
– Forms two daughter cells with complete set
of chromosomes.
Mitosis
Mitosis results in the production of
two cells that are genetically identical
to the original cell.
Mitosis has four phases/stages: “PMAT”
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
P
M
A
T
Mitosis
Cell Growth and Reproduction
1st Phase of Mitosis: PROPHASE
– Long stringy chromatin coils up into visible
chromosomes
Spindle fibers
Disappearing
nuclear envelope
Doubled
chromosome
Mitosis begins with the phase:
PROPHASE
Centrioles form
spindle and
Chromatin (DNA)
condenses into
paired
chromosomes.
Sister
chromatids
Mitosis second stage is
Metaphase!
The nuclear membrane
dissolves.
The centrioles move to
opposite ends while
forming the spindle.
The chromosomes line
up in the middle of
the cell.
Microtubules
Microtubules are small cylindrical fibers that change in length by
assembling (polymerizing) and disassembling (depolymerizing).
They are made of a protein called tubulin. Tubulin dimers are arranged
to form a long hollow cylinder.
The fibers are lengthened and shortened as tubulin dimers assemble
or disassemble from one or both ends of the filament.
The assembly of microtubules is controlled by an area near the
nucleus called the centrosome or microtubule organizing area..
Microtubules act as tracts along which organelles can move. For
example, they are associated with movement of vesicles from the
Golgi complex to the plasma membrane.
Microtubules are responsible for the movement of cilia and flagella.
They move the chromosomes during cell division in the spindle
apparatus.
Mitosis third stage is
Anaphase!
The chromatids
(daughter
chromosomes) are
pulled apart
by the spindle
and move to
opposite ends of
the cell.
Anaphase: Chromatids are pulled apart
Mitosis = Cell Division
#3 TELOPHASE
The nucleus
forms around
each identical
set of
chomosomes.
The spindle
disappears.
Share the same
cytoplasm.
Telophase: The newly divided animal
cell pinches itself off in the middle;
a plant cell forms a cell plate.
Cell Growth and Reproduction
CYTOKINESIS
The two identical
(daughter) cells
completely
separate and no
longer share a
membrane.
DNA forms into
chromatin again.
Cytokinesis in Plants is different than
Animals
What is
the
longest
phase of
the cell
cycle?
Mitosis=PMAT
Control of the Cell Cycle
What happens when MITOSIS goes
WILD?
– CANCER
Control of the Cell Cycle
Cancer:
– Malignant growth due
to uncontrolled cell
division.
– Genetic changes to
genes that control cell
growth.
– Caused by
environmental and
genetic factors.
Lung cancer cells (530x). These cells
are from a tumor located in the
alveolus (air sac) of a lung.
Control of the Cell Cycle
Cancerous cells form masses of tissues
called MALIGNANT tumors.
Tumors starve normal cells from
nutrients
Wait! But can’t I have a BENIGN
tumor?
– YES! Benign tumors are masses of
tissues that are harmless. (BENIGN =
HARMLESS)
– Created by slower growing cells that clump
together to form lumps.
Control of the Cell Cycle
Cancer: METASTASIS
– In later stages, cancer
spreads, enters
circulatory system, and
spreads throughout
body.
– Forms new tumors that
disrupt functions of
organs, organ systems,
and organism as a
whole.
Skin cancer cells with a
dividing cell stained red.