Stem Cells

Question 1

Genome

Answer 1

The genome refers to the complete set of genes, chromosomes or genetic material present in a cell or organism.

Question 2

Cellular differentiation

Answer 2

When an unspecialised stem cell changes and carries out a specific function in the body, the process is called cellular differentiation. Cells differentiate to form different cell types due to the expression of different genes.

Question 3

Emergent properties

Answer 3

According to emergent properties, a complex system possesses properties that its constituent parts do not have – the whole is more than the sum of its parts.

Question 4

Stem cell

Answer 4

A stem cell is an undifferentiated cell of a multicellular organism that can form more cells of the same type indefinitely, and from which certain other kinds of cells arise by differentiation.

Question 5

Totipotent stem cells, e.g. the eight cells of the morula (the first cells formed following fertilisation of an egg cell)

Answer 5

Can differentiate into any type of cell including placental cells.

Can give rise to a complete organism.

Question 6

Pluripotent stem cells (e.g. embryonic stem cells of the blastocyst)

Answer 6

Can differentiate into all body cells, but cannot give rise to a whole organism.
-pluripotent stem cells can only be taken from the inner cell mass of the blastocyst.

Question 7

Multipotent stem cells (e.g. umbilical cord stem cells)

Answer 7

Can differentiate into a few closely related types of body cell.

Question 8

Unipotent stem cells

Answer 8

Can only differentiate into their associated cell type. For example, liver stem cells can only make liver cells.

Question 9

Stargardt’s disease

Answer 9

Stargardt’s disease is an inherited form of juvenile macular degeneration that causes progressive loss of vision, ultimately leading to total blindness.

Question 10

Leukemia Treatment

Answer 10

Treatment in this case involves harvesting hematopoietic stem cells (HSCs), which are multipotent stem cells. HSCs can be taken from bone marrow, peripheral blood or umbilical cord blood. The HSCs may come from either the patient or from a suitable donor. The patient then undergoes chemotherapy and radiotherapy to get rid of the diseased white blood cells. The next step involves transplanting HSCs back into the bone marrow, where they differentiate to form new healthy white blood cells.

Question 11

Stargardt’s Treatment

Answer 11

Patients are given retinal cells derived from human embryonic stem cells, which are injected into the retina. The results obtained have been quite positive as the inserted cells attach to the retina and become functional, suggesting that it may be possible to restore sight to affected individuals using stem cells.

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Short answer:
Injecting retinal cells derived from human embryonic stem cells into the retina of patients suffering from Stargardt’s disease.

Question 12

Leukemia

Answer 12

Leukemia, a type of cancer of the blood or bone marrow, is caused by high levels of abnormal white blood cells.

Question 13

Uses for Stem Cells

Answer 13

• Cells may be used in cell therapy (replacing bad cells with good ones) to eliminate serious diseases or disabilities in the human population.
• Transplants can be easily obtained without requiring the death of another human or inflicting any kind of pressure on normal body functioning which happens when someone donates an organ.
• The stem cells are harvested from the embryo at an early stage when the embryo has not yet developed a nervous system and thus it is not likely to feel any pain.