There is no limit on the number of divisions it can do
There are different types of stem cell: Pluripotent and Totipotent.
Pluripotent Stem Cells can:
Give rise to many different cell types
Cannot give rise to embryonic cells
Some of the genes have been deactivated.
Totipotent Stem Cells can:
Give rise to all 216 cell tyoes
They are undifferentiated and unspecalised
They can keep dividing
All the genes have the potential to be active as no genes have been switched off.
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Specalisation
How to stem cells become differentiated cells?
A chemical stimulus is given to the unspecalised cells
This causes some genes to be switched on and become active and genes to be switched off.
mRNA is only made from active genes
The mRNA moves to the ribosomes.
The ribosomes read teh mRNA adn make the appropiate protein.
The protein can pernanently alter the structure and function of the cells.
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Sources of Stem Cells
Embryonic Stem Cells:
Advantages --> Easy to extract and grow
Disadvantages --> Ethical issues, possible rejection by patients body, risk of infection when cells recived, risk of stem cells becoming cancerous in body.
Adult Stem Cells:
Advantages --> Fewer ethical issues, rejection risk is avoided if stem cells are taken from the patient.
Disadvantages --> Difficult to extract, more difficult to produce different cell types, risk of infection when cells are extracted or recieved.
Fused Cells:
A nucleus taken from the patients body cell is inserted into a human cell with the nucleus removed. It divides to produce stem cells with the patients DNA.
Advantages -->Rejction risk avoided if nucleus is taken from the patient, there is a potential for treating genetic disorders.
Disadvantages --> Ethical issues with the source of embryonic nuclei, risk of infection when cells recieved, risk of stem cells becoming cancerous in body.
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Risks with recieving stem cells
Possible route to infection
Rejected by patient
Increased chance of the patient becoming cancerous
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