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IB Biology SL > 1: Stem Cells > Flashcards

1: Stem Cells Flashcards

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1
Q

Define stem cells. What are their two key qualities?

A
  1. cells that have the capacity to divide and differentiate along different pathways
  • Self renewal: They can continuously divide and replicate
  • Potency: They have the capacity to differentiate into specialised cell types
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2
Q

What do human embryos entirely consist of in their early stages?

A

embryonic stem cells

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3
Q

What happens to the stem cells in a human embryo as time goes on?

A
  1. they gradually commit themselves to a pattern of differentiation
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4
Q

Can a cell divide after it is committed?

A
  1. yes, several more times

2. but all of the cells formed will differentiate the same way so they are no longer stem cells

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5
Q

Are stem cells found in the adult body?

A
  1. yes in small numbers
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6
Q

Where are adult stem cells found?

A
  1. most human tissues including: skin, liver and bone marrow
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7
Q

To what extent can adult stem cells differentiate relative to embryonic stem cells?

A
  1. they do not have as great a capacity as embryonic stem cells
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8
Q

What do adult stem cells grant to tissues?

A
  1. considerable powers of regeneration because stem cells means the possibility to make new cells
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9
Q

Which tissues lack stem cells needed for effective repair?

A
  1. brain, kidney, heart
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10
Q

What might stem cells (probably embryonic) be used for?

A
  1. tissue repair

2. degenerative conditions e.g. Parkinson’s disease

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11
Q

What are ethics?

A
  1. moral principles that allow us to decide whether something is morally right or wrong
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12
Q

What should scientists always consider before doing research?

A
  1. ethics of the research

2. the consequences of the research

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13
Q

Give ethical argument in favour of use of stem cells.

A
  1. health and quality of life of patients suffering from incurable conditions may be greatly improved
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14
Q

What do ethical arguments against stem cell use depend on?

A
  1. the source of the stem cells (embryonic/adult)
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15
Q

How many objections are there to using adult stem cells? Explain.

A
  1. pretty much none

2. because adults can give informed consent

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16
Q

Can newborn babies give informed consent?

A
  1. duh
17
Q

If babies cannot give informed consent, how can it be ethical for us to harvest stem cells from them?

A
  1. their parents can give informed consent on their behalf
18
Q

Where are stem cells ‘harvested’ from in newborn babies?

A
  1. their umbilical cord
19
Q

What are the stem cells harvested from babies usually used for?

A
  1. stored in case they are needed during the babies subsequent life
20
Q

It seems that informed consent solves all ethical issues. Where might ethical issues involving stem cells be more controversial?

A
  1. stem cells taken from specially created embryos are more controversial
21
Q

Why are stem cells taken from specially created embryos (more) controversial?

A

some argue:

  1. embryo is a human life even at earliest stage
    - if the embryo dies as a result of the procedure, procedure is immoral
    - because a life has been ended the benefits from therapies using embryonic stem cells do NOT justify the taking of a life (nor the risk of taking a life)
22
Q

Consider the ‘embryo = human life’ argument against the use of embryonic stem cells. What are some counter-arguments (full version)?

A
  1. early stage embryos are nothing more than a little ball of cells, yet to develop essential features of human. Therefore, they are not human
  2. early stage embryos lack a nervous system so do not feel pain or suffer in other ways during stem cell procedures.
  3. if embryo is produced deliberately, no individual that would otherwise have had the chance of living is denied the chance of life
  4. large numbers of embryos produced by IVF are never implanted and do not get the chance of life; rather than kill these embryos it is better to use stem cells from them to treat disease and save lives
23
Q

Give two examples of diseases that can be treated with stem cells.

A
  1. Stargadt’s muscular dystrophy (embryonic stem cells)

2. Leukemia (adult stem cells)

24
Q

What is Stargadt’s muscular dystrophy?

A
  1. a genetic disease causing loss of vision
25
Q

Who does Stargadt’s muscular dystrophy usually affect?

A
  1. children

2. develops in children between the ages of 6 and 12

26
Q

What are most cases of Stargadt’s muscular dystrophy caused by?

A
  1. a recessive mutation of a gene called ABCA4
27
Q

What does the recessive mutation of the gene ABCA4 cause?

A
  1. causes a membrane protein used for active transport in retina cells to malfunction
  2. this means that photoreceptive cells degenerate and vision becomes progressively worse
  3. the loss of vision can be severe enough for the person to be registered as blind
28
Q

How is Stargadt’s muscular dystrophy being treated using stem cells?

A

researchers have developed methods for making….

  1. embryonic stem cells develop into retina cells

(remember that embryonic stem cells can differentiate along any pathway)

29
Q

How did scientists first test their cure for Stargadt’s muscular dystrophy?

A
  1. first experimented on mouse cells
30
Q

In 2010, a woman in her 50s with Stargadt’s disease was treated. How? What was the conclusion of the research?

A
  1. 50,000 retina cells derived fro embryonic stem cells were injected into her eyes
  2. the cells attached to the retina and remained their during the 4 month trial period
  3. there was an improvement in her vision and no harmful side effects
  4. further research needed but we can be optimistic about future treatment of Stargadt’s with embryonic stem cells
31
Q

What sort of disease is leukemia? What happens when a person has leukemia?

A
  1. cancer

2. abnormally large numbers of white blood cells are produced in the bone marrow

32
Q

What is a normal white blood cell count?

A
  1. 4,000 - 11,000 white blood cells / mm³
33
Q

What can the white blood cell count rise to in someone with leukemia?

A
  1. leukemia: above 30,000 white blood cells / mm³

2. acute leukemia: over 100,000 white blood cells / mm³

34
Q

How is leukemia treated?

A
  1. adult stem cells used
  2. large needle inserted into a large bone, usually the pelvis and fluid is removed from the bone marrow
  3. stem cells are extracted from this fluid and are stored by freezing them. They are adult stem cells so only have potential to produce blood cells
  4. high dose of chemotherapy drugs to kill all cancer cells in bone marrow. Bone marrow loses its ability to produce blood cells.
  5. Stem cell then returned to patient’s body. The cells re-establish themselves in the bone marrow, multiply and start to produce red and white blood cells.
  6. In many cases this procedure cures leukemia completely.

IB Biology SL (85 decks)

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