Stem Cells, Cell Differentiation and Communication in

Multicellular Organisms (like you!!!)

Stem Cell Basics

Unspecialized (undifferentiated) cells.

All of the stem cells contain the same DNA

Specific genes determine the type of cell

They have potential to become a specialized type (such as lung, liver, etc.)

They can also divide to create other stem cells

What is a stem cell?

Identical stem cells

Stem cell

SELF-RENEWAL(copying)

Stem cell

Specialized cells

DIFFERENTIATION(specializing)

Two Basic Types

Embryonic stem cells

Adult Stem cells

In the Beginning……. You were one of these! Male sperm fuses (fertilizes) an egg. This is the very first cell…….a Zygote (picture on the

right)!!!

After about 5 days, a blastocyst has formed……source of

embryonic stem cells

Embryonic Stem cells**Versatile

**Have not differentiated into any particular type of cell

**Can be created in a (fertility clinics)

** Can develop into each of the more than 200 cell types of the adult body (Called Somatic Cells)

Extracting Embryonic Stem Cells Destroys the Embryo……..creates controversy!!

When does life begin?

Adult Stem Cells

**Found throughout the body; bone marrow (left), muscle, skin, teeth, heart, gut, liver, fat cells, cord blood…..

**replace dying and damaged tissues

**Can only develop into limited types of cells

DNA and Differentiation

**You have 46 total chromosomes (left)

**A zygote‘s DNA contains the instructions needed to become an organism

**Each cell only uses part of your DNA to differentiate into specific body cells called somatic cells; lung, heart, bone, etc.

**Once specialized, they do not become stem cells again

Cell Communication….

Cells signal each other Send and receive “messages” Identify each other Signals from the environment or from other cells Proteins on the cell’s membrane is involved