7.3 Stem cells

Question 1

What are stem cells?

Answer 1

Undifferentiated cells which have the ability to differentiate into many different cell types

Question 2

Why does the potency of cells decrease over development?

Answer 2

Epigenetic changes switch off some genes for certain cell types
- Allow the cells to fulfil their role, but lose their ability to divide

Question 3

Define totipotent

Answer 3

• Can produce any cell type INCLUDING extra-embryonic membranes needed to form a new embryo
• Very early embryo when just a few cells are present
• Plant cells remain totipotent throughout life

Question 4

Define pluripotent

Answer 4

• Can produce any cell type EXCEPT extra-embryonic cells
• Inner cell mass of late embryo (blastocyst)

Question 5

Define multipotent

Answer 5

• Limited range of differentiation
• Adult stem cells, e.g bone marrow cells which form all types of blood cell

Question 6

Why are pluripotent cells the most useful in medical research compared to others?

Answer 6

• Potential to produce a wide range of cells
• More plentiful than totipotent cells
• Genes only found in totipotent cells are not relevant to treatment (e-e membranes)
• Easier to obtain than adult stem cells

Question 7

Benefits of using pluripotent cells in medicine

Answer 7

Potential to grow replacement organs and tissues
Treatment of disease - diabetes, MS

Question 8

Problems of using pluripotent cells in medicine

Answer 8

Possible rejection
Ethical issues - many people believe embryos are killed in the process, religions that believe life begins at conception
Could become cancerous
Risk of infection

Question 9

Benefits of adult stem cells in medicine

Answer 9

Avoids most ethical issues
Bone marrow transplants can restore blood cell production following cancer treatment

Question 10

How are differentiated fibroblasts reprogrammed to form iPS cells?

Answer 10

Introduction of certain genes can undo changes made during cell differentiation

Question 11

Benefits of iPS cells

Answer 11

• Can directly replaced those cells affected by a disease
• Can generate new types of cells that can be used in the lab to test the effectiveness and safety of drugs, reducing need for animal experimentation
• Avoids many ethical issues

Question 12

Problems with iPS cells

Answer 12

• Can promote cancer development
• Sometimes the cells are changed in a way that still causes rejection by the immune system
• Recent discoveries allow proteins to be used rather than genes which may be more reliable