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Cell Differentiation & Gene Expression. Introducing stem cells. A life story…. Stem cells cells that can differentiate into a variety of specialized cell types. What is a stem cell?. stem cell. SELF-RENEWAL (copying). DIFFERENTIATION (specializing). specialized cell

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Cell Differentiation & Gene Expression

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A life story…

Stem cells

cells that can differentiate into a variety of specialized cell types


What is a stem cell?

stem cell





specialized cell

e.g. muscle cell, nerve cell

stem cell


What is a stem cell?

Stem cell

Stem cell





Identical stem cells

Specialized cells


Why self-renew AND differentiate?

1 stem cell

4 specialized cells

1 stem cell

Differentiation - replaces dead or damaged

cells throughout your life

Self renewal - maintains the stem cell pool


Where are stem cells found?

tissue stem cells

fetus, baby and throughout life

embryonic stem cells

blastocyst - a very early embryo

  • Types of stem cells:
  • Embryonic stem cells
  • Tissue stem cells

Embryonic stem (ES) cells:

Where we find them


cells inside

= ‘inner cell mass’

fluid with nutrients

culture in the lab

to grow more cells

embryonic stem cells taken from

the inner cell mass

outer layer of cells

= ‘trophectoderm’


Stem cell jargon

PotencyA measure of how many types of specialized cells a stem cell can make.

PluripotentCan make all types of specialized cells in the body Embryonic stem cells are pluripotent.

MultipotentCan make multiple types of specialized cells, but not all types

Tissue stem cells are multipotent.


Embryonic stem (ES) cells:

What they can do


embryonic stem cells


Embryonic stem cells are exciting because they can make all the different types of cell in the body – scientists say these cells are pluripotent.

all possible types of specialized cells


Embryonic stem (ES) cells:



grow under conditions A

grow under conditions B


embryonic stem cells

grow under conditions C


grow under conditions D




Tissue stem cells:

Where we find them

surface of the eye




intestines (gut)


bone marrow



Tissue stem cells:

What they can do

blood stem cell


found in

bone marrow

only specialized types of blood cell:

red blood cells, white blood cells, platelets


Tissue stem cells can ONLY make the kinds of cell found in the tissue they belong to. So, blood stem cells can only make the different kinds of cell found in the blood. Brain stem cells can only make different types of brain cell. Muscle stem cells can only make muscle cells. And so forth.

cell differentiation
Cell Differentiation

Cell differentiation – process of converting stem cells into more specialized cell types in multicellular organisms

  • Examples: muscle cells, liver cell, red blood cells
cell differentiation1

When does cell differentiation occur?

    • Development of a zygote into a full
    • organism
    • Tissue repair
    • Normal cell turnover
  • All of these require the repeated division and differentiation of stem cells.

Cell Differentiation

what is gene expression
What is gene expression?

Gene expression is the activation of a gene that results in a protein & is a very controlled regulated process.

why are all our cells different
Why are all our cells different?
  • They EXPRESS different portions of the genetic code (genes).
  • This means that different proteins are made by different cells causing them to look and function differently.
how does gene expression make our body cells different
How does Gene Expression make our body cells different?
  • Every cell in our body has the same 30,000 genes, but each cell selectively activates (“turns on”) certain genes
how do you think a gene expresses itself

The information on DNA (activated genes – those that are “turned on”) is translated into an organism's traits by producing specific proteins.

How do you think a gene expresses itself?


why are twins not exactly alike

Environmental factors such as temperature, pH, and availability of nutrients can influence the genes expressed in a cell.

Genes + Environment = Trait

Why are twins “not exactly” alike?

himalayan rabbits
Himalayan Rabbits
  • If a small section of fur is shaved from a Himalayan Rabbit, the fur will grow back either white or black depending on the temperature of its environment .



  • How does the environment affect hydrangea growth?
  • Depending on the pH of the soil, Hydrangea can range in color from blue to pink.
gene expression

All the cells in our body have the exact same DNA because they all came from a single cell which replicated its DNA

Although every cell in your body has the same DNA, not all cells are the SAME. Why?

Gene Expression