Stem Cells

Question 1

what is differentiation?

Answer 1

the process of a cell becoming specialised.

Question 2

do all cells in the body have the same DNA?

Answer 2

yes.

Question 3

why does the activity of stem cells have to be strictly controlled?

Answer 3

• if they do not divide fast enough then tissues are not efficiently replaced - leading to ageing.
• if there is uncontrolled division they form masses of cells called tumours - which can lead to cancer.

Question 4

what is stem cell potency?

Answer 4

a stem cells ability to differentiate into different cell types

Question 5

what does totipotent mean?

Answer 5

these stem cells can differentiate into any type of cell.

Question 6

which cells are totipotent?

Answer 6

• fertilised egg
• first 8 or 16 cells divided from fertilised egg

Question 7

what does pluripotent mean?

Answer 7

these can form all tissue types but not whole organisms.

Question 8

where are pluripotent stem cells found?

Answer 8

in early embryos

Question 9

what does multipotent mean?

Answer 9

can only form a range of cells within a certain type of tissue.

Question 10

what is an example of a multipotent stem cell?

Answer 10

haemotopoetic stem cells in bone marrow.

Question 11

what is the lifespan of an erythrocyte?

Answer 11

120 days - due to the lack of nucleus

Question 12

where are all blood cells derived from?

Answer 12

stem cells present in the bone marrow.

Question 13

what are the sources of animal stem cells?

Answer 13

• embryonic stem cells
• tissue (adult) stem cells.

Question 14

what are embryonic stem cells?

Answer 14

• totipotent
• present at early stage of embryo development.
• after 7 days a mass of cells (blastocyst) has formed and cells are in pluripotent state. remain this way till birth

Question 15

what are tissue stem cells?

Answer 15

• multipotent.
• invasive surgery is not needed.

Question 16

where are stem cells present in plants?

Answer 16

meristematic tissue.

Question 17

where is meristematic tissue found?

Answer 17

• wherever growth is occuring in plants, tips of roots and shoots.
• vascular cambium sandwhiched between phloem and xylem tissue. vascular tissue grows as the plant grows.

Question 18

what are the potential uses of stem cells?

Answer 18

• heart disease
• type 1 diabetes
• parinson’s disease.
• alzheimers disease
• macular degeneration
• birth defects
• spinal injuries

Question 19

what are stem cells currently being used for?

Answer 19

• treatment of burns
• drug trials
• developmental biology.

Question 20

what are the negatives of stem cells?

Answer 20

• removal of stem cells from embryos normally results in the destruction of embryos.
• religous objections to the use of embryos; many people believe that life begins at conception and the destruction of embryos is murder.

Question 21

why are adult stem cells not as good as umbilical stem cells?

Answer 21

• they do not divide as well.
• more likely to have acquired mutations.