Stem Cells

Question 1

What is a stem cell?

Answer 1

It is a cell that can both duplicate itself (self-renew) and make other types of cells that become the specialized cells of the body (differentiate).

Question 2

Self-renewal

Answer 2

• When a cell makes copies of itself
• It’s important because if they didn’t self-renew, you would quickly run out of stem cells

Question 3

Differentiation

Answer 3

• When a cell makes other types of cells that become the specialized cells of the body
• It’s important because specialized cells cannot self-renew, so stem cells make more by differentiation

Question 4

Specialized cells

Answer 4

• Cells that are needed for a specific function of the body
• They go where the need is greatest
• They cannot divide and make duplicates of themselves

Question 5

Where are stem cells found?

Answer 5

• Embryonic stem cells are found in a blastocyst (a very early embryo)
• Tissue stem cells are found in a fetus, in the baby, and throughout life

Question 6

What are stem cells called in plants?

Answer 6

Meristematic cells

Question 7

Where are stem cells found in plants?

Answer 7

All the places where the plant grows, such as the tips of the stems, leaves and roots

Question 8

Embryonic stem cells

Answer 8

• Found in blastocysts (very small, contain about 50-100 cells)
• They are taken from the inner cell mass and cultured in a lab to grow more of them
• They are pluripotent

Question 9

Tissue stem cells

Answer 9

• Found in the brain, breasts, intestines, bone marrow, muscles, testicles, skin, and on the surface of the eye
• They are multipotent

Question 10

Induced pluripotent (iPS) stem cells

Answer 10

• ‘Genetic reprogramming’, add certain genes to the cell
• Discovered in 2006
• They use small animals for testing because they reproduce faster
• They culture iPS cells in a lab until they undergo differentiation and become all possible types of specialized cells
• Scientists add certain genes to the iPS cells that make them behave like embryonic stem cells

Question 11

Pluripotent

Answer 11

Can make all types of specialized cells in the body

Question 12

Multipotent

Answer 12

Can make multiple types of specialized cells, but not all types

Question 13

Totipotent

Answer 13

Can differentiate into all types of specialized cells in the body PLUS cells that are needed during development of the embryo only: placenta, yolk sac, and umbilical cord

Question 14

Unipotent

Answer 14

Can only differentiate into one type of specialized cell (e.g. spermatogonial cells can only make sperm)

Question 15

Why can some organisms regenerate but humans can’t?

Answer 15

• Regeneration is blocked in humans primarily because scar tissue is formed after an injury.
• Humans have lost or altered the functionality of these regenerative genes during their evolution
• Tissues in complex organisms cannot regenerate as they are highly differentiated to perform specialized functions.

Question 16

What is the history of stem cell research in Canada?

Answer 16

• The existence of stem cells was proven in 1961 by Canadian scientists James Till and Ernest McCulloch. Their paper on what were then called colony-forming cells was the breakthrough that started stem cell science.