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?