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Cell Reproduction
1
Types of Cell Reproduction
Asexual reproduction involves a
single cell dividing to make 2 new,
identical daughter cells
Mitosis & binary fission are
examples of asexual reproduction
Sexual reproduction involves two
cells (egg & sperm) joining to make a
new cell (zygote) that is NOT
identical to the original cells
2
Cell Division in
Prokaryotes
3
Cell Division in Prokaryotes
 Prokaryotes such as
bacteria divide into 2 Parent
cell
identical cells by the
process of binary
fission
Chromosome
 Single chromosome
doubles
makes a copy of
itself
 Cell wall forms Cell splits
between the
chromosomes dividing
the cell
2 identical daughter cells
4
Prokaryotic Cell
Undergoing Binary Fission
5
Animation of Binary Fission
6
Asexual Reproduction in Eukaryotes
Three main types: all result in genetically
identical offspring.
1. Budding
2. Fragmentation
3. Vegetative Reproduction
7
Cell Differentiation
What makes us so different, but still the
same.
What is cell differentiation?
• cellular
differentiation is
the process by
which a less
specialized cell
becomes a more
specialized cell
type.
Why differentiate cells?
• Because the various cells of each plant
and animals need to perform different
functions!
– Differentiation dramatically changes a cell's
size, shape, membrane potential, metabolic
activity, and responsiveness to signals.
– Once an egg cell is fertilized and becomes a
zygote, mitosis produces MORE cells and
differentiation produces DIFFERENT cells that
eventually becomes tissues, organs, etc.
How do cells differentiate?
• Cellular differentiation almost never
involves a change in the DNA sequence
itself.
– Thus, different cells can have very different
physical characteristics despite having the
same genome
• These changes are largely due to highly
controlled modifications in gene
expression: this means that different
cells use different genes.
Muscle cells
• Muscle cells
are designed
to contract
and relax
allowing for
movement.
Nerve cells
• Nerve cells are
designed to
receive and
transmit
impulses from
one area to
another.
Blood
• Blood is
responsible
for
transportin
g various
materials to
and from
the cells.
•It also patrols the
body as part of the
defense system.
Introducing….stem cells!
What are stem cells?
• the body is made up of about 200 different kinds of
specialised cells such as muscle cells, nerve cells, fat cells
and skin cells
• all cells in the body come from stem cells
• a stem cell is a cell that is not yet specialised
• the process of specialisation is called differentiation
• once the differentiation pathway of a stem cell has been
decided, it can no longer become another type of cell on
its own
Why are stem cells special?
Stem cells can:
• self-renew to make more
stem cells
• differentiate into a
specialised cell type
Stem cells that can become many
types of cells in the body are
called pluripotent
Stem cells that can become
only a few types of cells are
called multipotent
Embryonic stem cells (pluripotent)
Tissue stem cells (multipotent)
Tissue stem cells
• often known as adult stem cells
• also includes stem cells isolated from fetal and cord blood
• reside in most tissues of the body where they are involved
in repair and replacement
Bone marrow
Kidney
Lung
• generally very difficult to isolate
• already used to treat patients (haematological malignancies,
diseases of the immune system)
Where do embryonic stem cells
come from?
• Donated excess IVF embryos
egg
Day 0
Inner cell mass
fertilised
egg
2-cell
8-cell
blastocyst
Day 1
Day 2
Day 3
Day 6
Images from www.advancedfertility.com
Embryonic stem cells
human embryonic stem cells
• derived from donated IVF
embryos
• can be grown indefinitely in
the laboratory in an
unspecialised state
• retain ability to specialise into
many different tissue types –
know as pluripotent
• can restore function in animal
models following
transplantation
Human embryonic stem cells can become any
cell in the body including these beating heart
cells