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• Zygote: fertilized cell
created by the union of
the egg and sperm
• Zygote divides into
Embryonic stem cells
23
chromosomes
– Potential to become
any type of cell
Egg Cell
• Average human:
– 100 trillion cells
– Over 200 types of
human cells
23
chromosomes
Stem cells
zygote
Determination
• Determination
– Few weeks into
development
– Genes program
the stem cell to
become a
specific cell
– Irreversible
Stem cells
Differentiation
• Differentiation
– Cells acquire the
structures &
functions of a
specialized cell
– Specific genes
activated
Quick Questions
• Do your muscle cells have the same DNA as your skin
cells?
Yes
• Do your skin cells have the same DNA as your brain cells?
Yes
• Do your brain cells have the same DNA as your liver cells?
Yes
• So if all your cells have the same DNA, how do they know
to do different jobs?
Stay tuned for the answer
Stem cell (soon to be muscle cell)
Gene A
Gene B
Gene C
Gene D
Gene E
Gene F
Gene G
These
If
theselight
cellsswitches
have theare
same
symbolic
DNA, of
how
thewill
genes
the top
inside
celleach
know
to become
stem
cell. a muscle cell?
Stem cell (soon to be nerve cell)
Gene A
Gene B
Gene C
Gene D
Gene E
Gene F
Gene G
Stem cell (soon to be muscle cell)
Gene A
ON
ON
Gene B
Gene C
ON
Gene D
Gene E
Gene F
Gene G
The proteins created in the top cell will cause the stem cell to become a
muscle cell….
During “differentiation”, certain genes are activated in
What do genes direct cells to create?
some
cells,created
but deactivated
in others.
The
proteins
in the bottom cell
will cause the stem cell to a
nerve cell.
Stem cell (soon to be nerve cell)
ON
ON
Gene A
Gene B
Gene C
ON
Gene D
Gene E
Gene F
Gene G
Differentiation
Brain cells
• Differentiation
– Cells acquire the
structures &
functions of a
specialized cell
– Specific genes
activated
Muscle
cells
Pancreas cells
Skin cells
Programmed cell death (apoptosis)
between the fingers & toes
Incomplete Apoptosis
(Webbed Toes)
• Cell: Basic unit
• Tissue: Group of cells
– 4 types
• Organ: Groups of
tissue
– Ex: Heart contains
muscle &
connectivetissue
• Organ System: Group
of organs working
together
– Respiratory System
• Organism: all organ
systems working
together
Epithelial
Tissue
Nerve
Tissue
Muscle
Connective
TissueTissue
•Transmit
protection
sheetsignals
of cells
•
electric
• Contracting
• Support the
cells
body
•Brain
skin, &
stomach
lining
•
Spinal
Cord
• Skeletal,
• Bone, fat,
cardiac
tendons
cells
YouTube Review:
Levels of Organization
1)
2)
3)
4)
What is a zygote?
What is the specific function of a stem cell?
How does “determination” differ from “differentiation”?
Cells are programmed to die during a process called
______.
5) From smallest to largest, name the 5 levels of organization.
6) Name the four types of tissues.
7) Which tissue is able to stretch and contract?
8) Which tissue transmits electric signals?
9) Which tissue covers and protects the body?
10) Which tissue connects the body?