Chapter 10: Cell Growth and Division
Key ideas:
•Why do cells have to divide?
•Summarize the steps of the cell cycle
•Compare the various types of asexual
reproduction.
Cell Size
• Cell size is not determined by the size
of an organism. (Most cells of a mouse
and giraffe are about the same size)
Exception:
nerve and
muscle
cells
10-1
Cell Size
• In most cases, organisms get larger
because they produce more cells,
not because their cells become
larger.
• So why don’t cells just get larger?
– There are 2 reasons . . .
?
10-1
Reason 1: DNA Overload
• The nucleus can control only a
limited amount of living, active
cytoplasm.
SO
Cells have to remain small.
10-1
Reason 2: Exchanging
materials
As cells get bigger, the
need for nutrients and
waste production increase.
Wastes have to get out, nutrients in.
10-1
Surface area-to-volume
ratio
As cell size increases,
volume increases faster
than surface area.
If the cell is too big,
it won’t be able to
get nutrients to
center of cell and
eliminate waste fast
enough. 10-1
10-2: Cell Division
Std: 7 1e: Cells divide to
increase their numbers through
mitosis. This results in 2
identical cells.
10-2
10-2: Cell Division
• When a cell reaches maximum size,
nucleus initiates cell division.
– splitting of 1 cell into 2 new
daughter cells
– 2 phases:
• Mitosis (division of the nucleus)
• Cytokinesis (division of the
cytoplasm)
10-2
Cell division
• The result of cell division is 2
identical daughter cells.
• In plants and animals (humans)
this begins right after
fertilization.
10-2
10-2
Important information has
to be passed from parent to
daughter cells.
• This information is carried in
chromosomes. (chrom’s)
• Every organism has a specific
number of chrom’s
10-2
Humans have 46 chromosomes
(23 pairs) in each body cell.
A hamster has 44 chrom’s
(22 pairs) in each body cell.
An onion has 16 chrom’s
(8 pairs) in each cell.
10-2
10-2
• Chromosomes only visible
during cell division.
• Before cell division begins,
genetic material must be
copied, or replicated.
– Replication creates 2 identical
chromatids.
10-2
Replicated chromosomes
Centromere
Chromatids
**Chromosomes only look like this before cell division**
10-2
1 Homologous chromosome pair
(1 from mom, 1 from dad)
Sister
chromatids


Centromere
Replication
10-2
Anatomy of a
chromosome
One from mom, one from dad
(homologous
pair)
Gene for brown eyes
}
Exact copies
(sister
chromatids)
}
Gene for blue eyes
10-2
The Cell Cycle has 6 Stages (phases):
• Interphase
• Prophase
• Metaphase
• Anaphase
• Telophase
• Cytokinesis
Mitosis is these
4 stages
10-2
10-2
Interphase
•
•
•
•
90% of cell cycle.
Animal
growth and development.
genetic material makes copy of itself.
organelles are made.
“Interphase: In-between”
Plant
10-2
10-2
Prophase
• Chromosomes become visible.
• Nuclear membrane disappears
“prophase party”
10-2
Metaphase
• Chromosomes align along middle
of cell.
“Metaphase:Middle”
10-2
Anaphase
• Centromeres divide
• sister chromatids pulled to opposite
ends of cell.
“Anaphase:Apart”
10-2
Telophase
• Nuclear membrane
forms.
• Cytoplasm divides
and 2 daughter cells
are formed.
New cells have same number of
chromosomes as original cell.
Cell plate
“Telophase:Two”
10-2
Cytokinesis
• Animal
vs.
plant
cells
• Animal: “pinching-in
of cell membrane.
• Plant: formation of
cell plate.
10-2
Cytokinesis
“pinching in”
Cell plate
The Cell Cycle
• Interphase
• “Prophase Party”
• “Metaphase Middle”
• “Anaphase apart”
• “Telophase TWO” and
Cytokinesis
“That’s the cell cycle broken down into
pieces.”
If no final division, you get a
multinucleated cell.

Muscle cells
fungi
20-1
Complete the following:
• When a cell reaches a certain size, the
nucleus initiates _________ ________.
• The life of a cell is composed of 6 stages
which are collectively called the ___ ___.
• Chromosomes are copied by a process
called: ______________.
• Mitosis is composed of ______ stages.
20-1
Repair
• Mending of damaged tissues
(regeneration).
20-1
Repair
20-1
Reproduction
• Asexual reproduction: reproduction
resulting from simple cell division.
Only
1
Parent
Offspring are genetically identical to parents
20-1
Asexual reproduction in animals
•
•
•
•
Sponges
Sea stars
Worms
Stem cell research
– Growing new organs from single cell?
– Cloning
• Sheep, cat, cattle, mule, deer
20-1
How does this
process of cell
division, which allows
growth, repair,
reproduction, occur?
How does cell division
happen?
20-1
20-2: Asexual Reproduction
20-2
Asexual reproduction
• Product of mitotic cell division
• Produces identical offspring
• Examples:
–Binary fission in bacteria
–Budding in yeast
–Regeneration
–Vegetative reproduction
20-2
Binary fission (bacteria)
20-2
Budding (yeast)
20-2
Regeneration
This is more
characteristic of
simple, rather than
complex organisms.
20-2
Vegetative propagation
(production of new plants)
20-2
Advantages of vegetative
propagation:
• Offspring exactly like parent (plants
grown from seed don’t always show
same traits as parents).
• Faster than from seed.
• Only way to propagate seedless
fruit!
1 Homologous chromosome pair
(1 from mom, 1 from dad)
Sister
chromatids


Centromere
Replication