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The Cell Cycle
Growth,
reproduction and
functions
Cell Cycle has Four Main Stages
•
•
•
•
Gap 1
Synthesis
Gap 2
Mitosis
What is Mitosis?
• Mitosis is the process in which a
eukaryotic cell separates the
chromosomes in its cell nucleus, into two
identical sets in two daughter nuclei
• Occurs exclusively in Eurkaryotic cells
Interphase
Parent cell
centrioles
spindle fibers
centrosome
nucleus with
DNA
Pnuemonic for Mitosis
People may answer telephones
• Prophase
• Metaphase
• Anaphase
• Telophase
It’s all Greek to Me
The word ‘phase’ = appearance
• Inter = between
• Pro = before
• Meta = after
• Ana = back
• Telo = end
What do you think the prefixes used are
referring to?
Appearance of chromosomes.
Cytokinesis
• The division of the cytoplasm and the
plasma membrane following the division of
the nucleus resulting into two cells, each
having its own nucleus and cytoplasm
surrounded by a plasma membrane.
Don’t confuse the Two
• Mitosis—division of cell nucleus
• Cytokinesis—division of cell cytoplasm results
in two cells each of which contain s one of the
nuclei from mitosis
Parent cell
mitosis
cytokinesis
daughter cells
CELL REPRODUCTION
STEPS OF INTERPHASE:
• G1 (Growth 1) phase:
--cell grows and is
metabolically active
--RNA and new proteins are
made
--energy is needed for these
things to occur
• S (Synthesis) phase
--DNA content of cell doubles
--genetic info is copied exactly
CELL REPRODUCTION
STEPS OF INTERPHASE:
• G2 (Growth 2) phase:
--another phase of growth and
metabolism
--RNA, proteins, etc are synthesized in
smaller amounts
--A substance is made that TRIGGERS
the start of cell division
CELL REPRODUCTION
STAGES OF MITOSIS
• PROPHASE:
--Chromatin condenses
down into chromosomes
--NUCLEAR ENVELOPE
disappears
--Spindle apparatus forms
and spindle fibers attach to
chromosomes
CELL REPRODUCTION
STAGES OF MITOSIS
• METAPHASE:
--Chromosomes
move to the center
of the cell
• ANAPHASE:
--Chromosome
strands pulled
toward poles
CELL REPRODUCTION
STAGES OF MITOSIS
• TELOPHASE:
--Chromosomes gather at poles
--NUCLEAR ENVELOPE reappears
--Organelles segregate
--Cytokinesis, division of
cytoplasm occurs
Cells divide at different rates
• It’s linked to the body’s need for those
cells.
• In humans—the S, G2 and M stages take
approximately 12 hours
Question?
• Do you think a skin
cell would have a long
or short G1 stage?
• A short G1 because
skin cells undergo a
lot of wear and tear
so they are replaced
quicker.
Cell size is limited
• What formula is used to calculate the surface
area of the cell?
Length x width x number of sides
• What formula is used to calculate the volume of
a cell?
Length x width x height
Rememer: the surface area of a cube increases
by the length squared and its volume increases
by length cubed.
5.2 Mitosis and Cytokinesis
DNA is made of four different subunits called nucleotides.
What would you do if you had to put a lot of clothes into a
small suitcase?
Compress the clothes
If you were sharing the suitcase with your twin sister or
brother, what would you need to do?
Compress the clothes, and later separate them
DNA needs to be both condensed and separated for a cell
to divide.
Chromosomes
organized structure of DNA and protein
• 1-Chromatid-one of two identical
parts of chromosome after S phase
• 2-Centromere-point where two
chromatids touch and microtubles attach
• 3-Short arm
• 4-Long arm
• Telomeres-repeating nucleotides that do not form genes;
prevent the ends of chromosomes from accidentally attach to one
another and help prevent the loss of genes.
Histones
• At almost all times
during the cell cycle,
chromosomes are
associated with
histones
• Act as spools with
which DNA winds
forming chromatin
• Major role in gene
regulation
DNA
double
helix
DNA
and
histo
nes
Chrom
atin
Supercoil
ed
DNA
Chromatin
“loose” combination of DNA and proteins that
makes up chromosomes—DNA is organized in
the cell by wrapping around histones at regular
intervals
Interactions between parts of the histones further
compact the DNA
Supercoiled DNA
• Chromatin coils more
and more tightly
around organized
proteins
Infer
• Overall, DNA has a negative charge. Look
at the histones figure on page 139 of your
book.
• What type of overall charge do you think
they have?
• Positive; negative and positive charges
attract. If the histones were negatively
charged, they would repel DNA
Apply
• What is the relationship
between a molecule of DNA
and a chromosome?
• A chromosome is made of one
continuous DNA molecule.
• DNA is organized in the cell by
wrapping around histones at
regular intervals
• Remember: two spiraling
strands of DNA double helix
represent a single molecule.
5.3 Regulation of the Cell Cycle
• External factors
--physical and
chemical signals
Example of physical
factor: cell-to-cell
contact
• Example of chemical factor:
Growth factor
Epidermal growth factor
Nerve growth factor
Internal Factors
• Kinases—(to move) enzyme that transfers
a phosphate group from one molecule to a
specific target molecule
• Cyclins-group of proteins that are rapidly
made and destroyed at certain points in
the cell cycle.
These factors help a cell advance to
different stages of the cell cycle.
Apoptosis
• Programmed cell death
Human Example: cells
between the webbed
digits in human embryo
die off resulting in
unwebbed fingers and
toes
Plant example: deciduous
tree leaves dropping off in
fall
Cell division is uncontrolled
in cancer
• Bladder Cancer cells
dividing
Breast cancer cell
Skin Cancer Cells
Leukema
Benign vs Malignant Tumors
Metastasize
• “break away,” “leak,” or “spill” from
primary tumor and enter lymph system
and blood vessels; circulate and then
settle into new tissue to grow
• Pancreatic cancer cells
all over parts of liver
Skin Cancer
Cancer Treatment
• Standard treatment involves both ionized
radiation and chemotherapy
• It works by damaging a cell’s DNA so
much that the cell cannot divide.
5.4 Asexual Reproduction
• Most prokaryotes reproduce through
binary fission (asexual reproduction of a
single-celled organism by division into
roughly equal parts).
•
parent cell
•
DNA duplication
•
cell begins to divide
•
daughter cells
Binary Fission
Advantages/Disadvantages of
Asexual Reproduction
Advantages:
• More efficient
• Produces a genetically identical offspring that is
well suited to their environment
• Don’t need to locate a mate (which uses energy)
Disadvantages:
Entire populations can die off if changes to
environment occur– no diversity
Eukaryotes
• Can reproduce asexually through mitosis
Examples:
Stem cutting for new plants
New arm on sea star
Doing it Both Ways
•
Sea Anemone
asexually--divides in half, by breaking
off small pieces from its base or by
budding
sexually—by producing eggs and sperm
5.5 Multicellular Life
• What are some of the different types of
cells in your hand?
• Those making up skin, hair, fingernails,
muscle, bone, blood, nerves
• Are the cells in the trunk of your body any
different?
• Similar types of cells, but in addition, many
more associated with internal organs.
Interactions among cell types
• Tissues
• Organs
• Organ Systems
Question?
• Suppose your family goes out of town and
forgets to ask your neighbor to water the
plants. Do you think the plants’ stomata
will be open or closed?
• Because the plants are not receiving
water, they need to conserve it. The
stomata will mostly likely be closed.
Cell
• Vessel elements are tube-shaped cells
Tissue Cell
• Vessel elements and tracheids form xylem
Organ
• Xylem and other
tissues form roots that
absorb water and
nutrients
Plant System
Cell Differentiation
• Process by which
unspecialized cells
develop into their
mature forms and
functions.
Stem Cells
repair system for body
Unique type of body cell
that have the ability to:
1) divide and renew themselves for long
periods of time
2) remian undifferentiated in form
3) develop into a variety of specialized cell
types
Stem Cell Classification
Mitosis vs Meiosis
• Show clip
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