Stem cells

Question 1

What are stem cells?

Answer 1

Stem cells are undifferentiated cells that can continually divide + become specialised. Differentiation is the process where stem cells become specialised
Different types of stem cells that have different differentiation abilities: totipotent, pluripotent, multipotent, unipotent stem cells

Question 2

Totipotent stem cells

Answer 2

Stem cells that can divide + produce any type of body cell.
Occur only for a limited time in early mammalian embryos

Question 3

Pluripotent stem cells

Answer 3

Found in embryos + can divide into almost every cell (but not the placenta cells)
Can divide into unlimited numbers + are used in treating human disorders
There’s issues with this as sometimes the treatment doesn’t work or the stem cells continually divide to create tumours. Ethical issues- whether its right to make a therapeutic clone of yourself to make an embryo to get the stem cells to cure a disease + then destroy the embryo

Question 4

Multipotent + unipotent stem cells

Answer 4

Found in mature mammals + can divide to form a limited number of different cell types
Multipotent cells- differentiate into a limited number of cells e.g multipotent cells in bone marrow can only make RBC’s
Unipotent cells can only differentiate into one type of cell + are used to make cardiomyocytes

Question 5

Induced pluripotent stem cells (iPS cells)

Answer 5

Can be produced from adult somatic cells (body cell) using appropriate protein transcription factors to overcome some of the ethical issues with using embryonic stem cells
Created from adult unipotent cells + these cells can be from almost any body cell + altered in the lab to return them to a state of pluripotency. To do this, the genes that were switched off to make the cell specialised must be switched back on - done using transcriptional factors
Don’t cause destruction to embryo + adult can give permission. iPS cells can divide indefinitely to give limitless supplies so could be used in medical treatment