Unit 7- Stem Cells Flashcards

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1
Q

What is the potency and source of totipotent stem cells?

A
  • found in zygote/very early embryo (8 cell divisions)

- are able to produce any type of cell including extra embryonic membranes to form more embryo

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2
Q

What is the potency and source of pluripotent stem cells?

A
  • found in blastocyst inner cell mass

- can produce any cell type except extra embryonic membrane, so can’t form a new embryo

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3
Q

What is the potency and source of multipotent stem cells?

A
  • found in most adult tissue

- can produce a limited range of related cell types

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4
Q

What is happening to cells when they change from totipotent to pluripotent etc

A

Epigenetic changes to cells switch off particular genes for cell types reducing the potency

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5
Q

Give an example of a multipotent stem cell, and what is can differentiate into

A

Bone marrow cells

- may form red blood cells, white blood cells and platelets

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6
Q

How can we get hold of embryo stem cells?

A
  • in IVF, embryos are created and inserted into the mother

- there are inevitably spare embryos which contain pluripotent stem cells

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7
Q

What are the advantages and disadvantages of extracting pluripotent stem cells from embryos?

A

+ ability to produce almost all types of cells, potential to grown replacement organs and tissues
+ provision of cells for drug testing can replace the need for animal testing
- possible rejection of cells by immune system as the cells aren’t from then patient
- ethical issues of killing an embryo

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8
Q

What are the ethical views for and against using embryonic stem cells donated from fertility centres?

A
  • some religions consider human life and rights to start at conception
  • embryos cannot give consent
  • killing an embryo is no different from killing a person
    + potential benefits outweigh harm
    + banking cell embryos now will reduce future need for them
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9
Q

Where are adult stem cells obtained, and what potency are they?

A
  • most body tissues contain a small number of adult stem cells
  • these are multipotent
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10
Q

Issues and benefits of adult stem cells

A
  • stem cells won’t get rejected of they are from the patient
  • difficult to find and culture for transfer
  • not all cell types have adult stem cells
  • in bone marrow transplants the implanted white blood cells may damage the recipient
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11
Q

Describe how cells can become induced pluripotent stem cells

A
  • genes are inserted into fibroblasts using retroviruses
  • the genes code for transcription factors which reprogrammed the fibroblast to undo changes made in cell specialisation to become pluripotent stem cells
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12
Q

What kind of cells can be reprogrammed into IPS cells? And what are they?

A

Fibroblasts

- cells found in skin and other tissues

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13
Q

What are the issues of using IPS cells?

A
  • the genes used can promote cancer development

- sometimes the cells are changed in a way that still causes rejection by own immune system

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14
Q

How does use of IPS cells avoid ethical issues?

A

No killing of embryos

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15
Q

Identical twins develop when a single embryo splits into 2 in early development. Explain the observation that a split in the first few hours results in each embryo having its own placenta but a split after reaching the uterus results in embryos sharing a placenta

A
  • early embryos have totipotent cells, which can form a placenta in each new embryo
  • cells are pluripotent by the time they reach the uterus because of epigenetic changes
  • both embryos in a later split depend on cells that can’t differentiate into more placental tissue as they are no longer totipotent, therefore they share the placenta they already have
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