Formative Test - Biology > Cell Cycle; Stem Cells & Ethics (p3)

What are stem cells?

Stem cells are undifferentiated e.g. they have not yet developed into cells the preform a specific function

Definition and example of a totipotent stem cell:

Definition and example of a pluripotent stem cell:

Definition and example of a multipotent stem cell:

Definition and example of a oligopotent stem cell:

Definition and example of a unipotent stem cell:

What happens to each daughter cell when a stem cell divides?

1. Stay as a stem cell (self-renewal). This ensures there is an adequate supply of stem cells.

2. Becomes stem cell (differentiated). Once differentiated (e.g. liver cells) can’t be normally reverted to an undifferentiated state

What are embryonic stem cells:

• Embryonic stem cells are taken from the inner cell mass of a blastocyst

• A single cell is isolated and grown in culture, dividing to form more stem cells

• They are usually sourced from excess embryos created during IVF

• Removing these cells destroys the embryo

What are adult (stomatic) stem cells:

• Adult (somatic) stem cells are found in many parts of the body (e.g. bone marrow, skin, liver, brain, fat, and blood)

• They can also be collected from umbilical cord blood after birth

• They are multipotent, meaning they can develop into a limited range of specific cell types (e.g. blood or skin cells)

What are induced pluripotent stem cells

• Some specialised adult somatic cells can be genetically reprogrammed to return to an undifferentiated embryonic state.

Sources of stem cells table:

What are adult stem cell transplants?

• Stem cell transplants (therapy) are mainly used to treat blood disorders like leukaemia

• Leukaemia is treated with chemotherapy and radiation to destroy diseased cells

• These treatments also destroy healthy cells

• Injected stem cells help replace and rebuild healthy blood cells afterwards

What is therapeutic cloning?

• Therapeutic cloning creates an embryo to produce stem cells genetically identical to the patient

• These cells are reprogrammed to form specific tissue types needed for treatment

• It is legal in some countries, including the UK and Australia

How can therapeutic cloning be used?

Therapuetic cloning may someday be used in humans to:

1. Produce whole organs from single cells

2. Produce healthy cells that can replace damaged cells in degenerative diseases such as Alzheimer’s or Parkinson’s

Ethics of therapeutic cloning: Advantages vs disadvantages

• Reduced risk of rejection (patient’s own cells) vs Ethical/religious concerns and embryo destruction

• No need for a donor vs Concerns about cloning and lack of global agreement

• Can become any tissue type (pluripotent) vs Risk of tumour formation if misused

• Useful for studying diseases and testing treatments