Stem Cells

Question 1

What is differentiation?

Answer 1

• the process of a cell becoming specialised

Question 2

What is a stem cell?

Answer 2

• undifferentiated/unspecialised cell that can turn into any cell

Question 3

What is an undifferentiated cell?

Answer 3

• not adapted to any particular function

- have potential to differentiate into one of the range of specialised cells

Question 4

What problems can the division of stem cells cause?

Answer 4

• if they don’t divide fast enough tissues are not efficiently replaced leading to ageing
• if there is uncontrolled division they form masses of cells called tumours which can develop into cancers

Question 5

What is potency?

Answer 5

• a stem cells ability to differentiate into different cell types
• greater number of cell types it can differentiate into the greater the potency

Question 6

What is a totipotent stem cell?

Answer 6

• differentiate into any type of cell
• a fertilised egg, zygote and the 8 or 16 cells from first few mitotic divisions are totipotent cells
• also differentiate into extra-embryonic tissues like the amnion and umbilicus

Question 7

What is a pluripotent stem cell?

Answer 7

• can form all tissue types but not whole organisms

- present in early embryos

Question 8

What is a multipotent stem cell?

Answer 8

• only form a range of cells within a certain type of tissue

- haematopoetic stem cells in bone marrow is an example because they give rise to various types of blood cell

Question 9

What is the benefit of being a multicellular organism?

Answer 9

• groups of cells with different functions working together as one unit can use resources more efficiently than single cells operating on their own

Question 10

Where are blood cells derived from?

Answer 10

• stem cells in the bone marrow

Question 11

How long do neutrophils live? How many do stem cells produce an hour?

Answer 11

• about 6 hours

- 1.6 billion per kg per hour (figure increase during infection)

Question 12

What are the two main sources of animal stem cells?

Answer 12

• embryonic stem cells

- tissue (adult) stem cells

Question 13

What potency is an embryonic stem cell?

Answer 13

• totipotent at early stage of embryo development
• after about 7 days a blastocyst (mass of cells) has formed and the cells are now pluripotent.
• remain pluripotent in the foetus until birth

Question 14

What potency is an adult stem cell?

Answer 14

• multipotent, but growing evidence they can be artificially triggered to become pluripotent

Question 15

How can adult stem cells be restored?

Answer 15

• specific areas like bone marrow

- umbilical cord

Question 16

Where are plant stem cells found?

Answer 16

• in meristematic tissue
• tissue found wherever growth is so for example at the tips of roots and shoots
• also found between phloem and xylem tissues. This is called vascular cambium.

Question 17

What diseases can stem cells be used to treat?

Answer 17

• heart disease (some success)
• type 1 diabetes (some success)
• Parkinson’s disease
• Alzheimer’s disease
• macular degeneration (early results encouraging)
• birth defects (some success)
• spinal injuries (some success)

Question 18

How are Parkinson symptoms produced and does stem cell treatment work?

Answer 18

• shaking and rigidity caused by death of dopamine producing cells in the brain
• drugs currently only delay progress

Question 19

What is Alzheimer’s and does stem cell treatment work?

Answer 19

• brain cells destroyed as a result of build up of abnormal proteins
• drugs only alleviate symptoms

Question 20

How can stem cells be used to treat burns?

Answer 20

• they’re grown on biodegradable meshes and can produce new skin for burn patients
• quicker than taking graft from another part of the body

Question 21

How can stem cells be used in drug trials?

Answer 21

• drugs can be tested on cultures of stem cells before on animals and humans

Question 22

What are the objections of using stem cells from embryos?

Answer 22

• religious
• moral: life begins at conception and so destruction of embryo is murder, lack of consensus when embryo has rights and who owns the genetic material that is being used.

Question 23

What is the disadvantage of using umbilical cords over embryonic stem cells?

Answer 23

• multipoint, not pluripotent so restricts use

Question 24

What is the disadvantage of using adult stem cells?

Answer 24

• don’t divide as well as umbilical stem cells

- more likely to have acquired mutations

Question 25

What are induced pluripotent stem cells?

Answer 25

• iPSCs

- adult stem cells genetically modified to act like embryonic stem cells and so are pluripotent.

Question 26

Why is the use of stem cells called regenerative medicine?

Answer 26

• stem cells divide and specialise

- damaged tissue replaced