CELL DIFFERENTIATION&
GENE EXPRESSION
Introducing stem cells
A life story…
Stem cells cells that can differentiate into a variety of specialized cell types
stem cell
What is a stem cell?
stem cell
SELF-RENEWAL(copying)
specialized celle.g. muscle cell, nerve cell
DIFFERENTIATION(specializing)
What is a stem cell?
Identical stem cells
Stem cell
SELF-RENEWAL(copying)
Stem cell
Specialized cells
DIFFERENTIATION(specializing)
1 stem cell
Self renewal - maintains the stem cell pool
4 specialized cells
Differentiation - replaces dead or damagedcells throughout your life
Why self-renew AND differentiate?1 stem cell
Where are stem cells found?
embryonic stem cellsblastocyst - a very early
embryo
tissue stem cellsfetus, baby and throughout life
Types of stem cells:1) Embryonic stem cells2) Tissue stem cells
Embryonic stem (ES) cells:Where we find them
blastocyst
outer layer of cells= ‘trophectoderm’
cells inside = ‘inner cell mass’
embryonic stem cells taken fromthe inner cell mass
culture in the labto grow more cells
fluid with nutrients
Stem cell jargon
Potency A measure of how many types of specialized cells a stem cell can make.
Pluripotent Can make all types of specialized cells in the body Embryonic stem cells are pluripotent.
Multipotent Can make multiple types of specialized cells, but not all typesTissue stem cells are multipotent.
Embryonic stem (ES) cells:What they can do
embryonic stem cells
PLURIPOTENT
all possible types of specialized cells
differentiation
Embryonic stem cells are exciting because they can make all the different types of cell in the body – scientists say these cells are pluripotent.
neuronsgrow under conditions B
Embryonic stem (ES) cells:Challenges
embryonic stem cells
skin
grow under conditions A
blood
grow under conditions C
liver
grow under conditions D?
Tissue stem cells:Where we find them
muscles
skin
surface of the eye brain
breast
intestines (gut)
bone marrow
testicles
Tissue stem cells:What they can do
MULTIPOTENT
blood stem cell
found in bone marrow
differentiation
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.
A STEM CELL STORY
http://www.youtube.com/watch?v=2-3J6JGN-_Y#t=36
Cell Differentiation
Examples: muscle cells, liver cell, red blood cells
Cell differentiation – process of converting stem cells into more specialized cell types in multicellular organisms
CELL DIFFERENTIATIONWhen does cell differentiation occur?
oDevelopment of a zygote into a full organismoTissue repairoNormal cell turnover
• All of these require the repeated division and differentiation of stem cells.
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?• 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?
•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.
Protein
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
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 .
COLDHOT
Hydrangea• 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?