stem cells

Question 1

unique features of ALL stem cells

Answer 1

• unspecialised
• capable of undergoing proliferation and (long-term) self-renewal
• retains potential to differentiate to produce specialised cells
  upon receiving appropriate molecular signals

Question 2

different types of potency

Answer 2

• definition: the range of cell types to which a stem cell can give rise to
• types:
  
  • totipotent:
    
    • gives rise to all cell types that make up an organism
    • e.g. zygotes stem cells
  • pluripotent:
    
    • gives rise to cell types that develop from the 3 germ layers (mesoderm, endoderm, ectoderm)
    • cannot give rise to cells that form the extra-embryonic membrane (e.g. placenta)
    • e.g. embryonic stem cells (ESCs)
  • multipotent:
    
    • gives rise to limited number of cell types
    • e.g. adult stem cells like blood/hematopoietic stem cells

Question 3

committed stem cells

Answer 3

• set cells which have a more limited pathway of development are will differentiate to produce a specific group of cells
• include multipotent and unipotent stem cells

Question 4

progenitor / precursor cell

Answer 4

• derived from committed multipotent stem cells
• are partly differentiated cells that divide and give rise to differentiated cells

Question 5

significance of mitotic division for stem cells

Answer 5

• preserves population of undifferentiated cells
• while steadily producing a stream of differentiating cells

Question 6

defining properties of ESCs

Answer 6

• unspecialised
• capable of long-term self renewal
• maintain stable, full, normal complement of chromosomes (i.e. 2 complete sets)
• easy to obtain pure and can be cultivated in large numbers

Question 7

how HSCs work

Answer 7

Hematopoietic stem cells (aka blood stem cells)
-> (a) common lymphoid progenitor cell or
(b) common myeloid progenitor cell
-> (a) lymphoid lineage or
(b) erythroid and myeloid lineage
->(a) B and T lymphocytes or
(b) red blood cells and platelets (from erythroid),
rest of the white blood cells (e.g.neutrophils) (from myeloid)

Question 8

function of HSCs

Answer 8

replace blood cells

Question 9

ethical implications of using ESCs in research

Answer 9

• presence of moral dilemma:
  duty to prevent or alleviate suffering vs
  duty to respect value of human life
• especially in regards to the source of ESCs
• answer hinges on how we view the embryo
  
  • whether it has the status of a person
  • from which point on does it have this moral status

Question 10

how is iPSCs used in research

Answer 10

• human induced pluripotent stem cells (iPSCs) allows specialised adult cells from patient themselves to be genetically “reprogrammed“ to assume a stem cell-like state

Question 11

ethical, safety, efficacy

comparing use of iPSCs vs ESCs in research

Answer 11

• overcomes moral dilemma relating to duty to respect value of human life
• provides a source of patient-specific specialised cells
  -> recognised by patient’s body and not rejected
  => safer
• more time-consuming and slow (lower efficacy) as well as costly

Question 12

similarities between cancer cells and stem cells

Answer 12

• both can undergo self-renewal for long periods of time
• both have active telomerase and thus do not undergo replicative senescence

Question 13

how does stem cells account for principles of cell theory

Answer 13

accounts for the principles of
- living organisms are made up of one or more cells
- all cells come from pre-existing cells

since
- all cells in an organism are produced by mitosis and differentiation of stem cells
- where stem cells themselves also arise from stem cells
(e.g. totipotent stem cells give rise to pluripotent stem cells which then give rise to multipotent stem cells)
(e.g. totipotent stem cells give rise to all cell types)