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Early Embryonic Development
Stem Cells
Stem Cells – Part 1
The Information
What are they?
Where do we get them from?
Are they all the same?
Why are we interested in them?
How cells become specialised
• Correct stimulus is given to unspecialised cells
e.g. a chemical stimulus
• Some genes are switched on and become
active; other genes are switched off
• m-RNA is made from the active genes
• m-RNA moves to the ribosomes; the
ribosomes read the m-RNA and the
appropriate protein is made
• The protein can permanently alter the
structure and function of cells
Stem Cells – What are they?
.
A type of source or
master cell that can
........
.
Undifferentiated cells
Which keep dividing
And can give rise to other cell types
Potency
•
•
•
•
How much stem cells differentiate is called
potency
Stem cells vary in their potency:
Totipotent: can give rise to any cell and so can
produce a whole organism
Pluripotent: potential to develop into many cell
types but not all of them.
Multipotent: cells retain the capacity to make a
few types of cell
Unipotent: make one type of cell e.g. Skin cells
What are they and where are they
found?
Timeline of development
• Day 1: Fertilisation – a zygote is formed
Series of rapid cell divisions
No increase in size
• Day 5: Blastocyst – a hollow ball of cells
Outer layer
Placenta
Inner 50 cells
Embryo
• Week 12: Fully differentiated foetus.
Stem cells and their use in medicine
Sources of stem cells:
•Multipotent cells from adults
•Spare embryos from IVF
(pluripotent)
•Umbilical cord stem cells
•Therapeutic cloning or
admixed embryos
http://www.wellcome.ac.uk/Aboutus/Policy/Spotlight-issues/Human-Fertilisationand-EmbryologyAct/Humanadmixedembryos/index.htm
Different view points
Just a last point....
Ethical considerations
• Where do you stand on the issue of using
embryonic stem cells?
• What are the advantages and disadvantages
of using them in research?