Stem Cells

What are stem cells?

Undifferentiated cells that can divide and give rise to other cell types

What does undifferentiated mean?

Cells that are not specialised

What is differentiation?

The process by which cells become specialised

What are totipotent stem cells?

Stem cells that can form all cell types including extra embryonic cells

What extra embryonic structures can totipotent cells form?

The placenta

Where are totipotent stem cells found?

In the early embryo

What is the early embryonic stage containing totipotent cells called?

The blastomere stage

What are embryonic stem cells?

Totipotent stem cells found in early embryos

Are totipotent cells initially specialised?

No, they are unspecialised

What do totipotent cells eventually form?

Tissues that make up the foetus

What causes stem cells to differentiate?

Changes in gene expression

How does gene expression change during differentiation?

Some genes are switched on and others are switched off

What are pluripotent stem cells?

Stem cells that can form any body cell but not extra embryonic cells

Where are pluripotent stem cells found?

In the early stages of the embryo

Why can pluripotent cells not form a whole organism?

They cannot form extra embryonic tissues

What are pluripotent stem cells used for?

Replacing damaged tissues in medical treatments

What are multipotent stem cells?

Stem cells that can differentiate into a limited range of cell types

Give examples of where multipotent stem cells are found

Bone marrow and umbilical cord

What are unipotent stem cells?

Stem cells that can only differentiate into one cell type

How are stem cells classified?

By their ability to differentiate

What is the hierarchy of stem cell potency?

Totipotent, pluripotent, multipotent, unipotent

What are induced pluripotent stem cells (iPS)?

Pluripotent stem cells created from unipotent cells

How are induced pluripotent stem cells made?

By reprogramming gene expression in unipotent cells

Why are iPS cells useful?

They can be used without using embryos