Stem Cells and Differentiation

Question 1

what is the definition of a stem cell? (2)

Answer 1

• unspecialised cell that can self-renew

* can differentiate into specialised cell types

Question 2

what is the definition of potency?

Answer 2

the capability a stem cell has of differentiating into different cell types

Question 3

what are 4 levels of potency?

Answer 3

• totipotent - gives rise to embryonic membrane (ie. placental cells) AND all adult cell types
• pluripotent - gives rise to all adult cell types (inner cell mass of blastocyst)
• multipotent - gives rise to tissue-specific cell types
• unipotent - gives rise to 1 specific cell type

Question 4

from what stem cell are all blood cells derived?

Answer 4

multipotent haematopoietic stem cells in red bone marrow

Question 5

what type of cell division do stem cells undergo?

Answer 5

asymmetric cell division - gives another stem cell (self-renewal) and a more specialised cell

Question 6

what are the haematopoietic progenitor cells?

Answer 6

lymphoid and myeloid (cell lineages)

Question 7

what are some common cells of the myeloid lineage? (6)

Answer 7

erythrocytes, megakaryocytes, monocytes, neutrophils, eosinophils and basophils

Question 8

what are some common cells of the lymphoid lineage? (3)

Answer 8

B lymphocytes, T lymphocytes and natural killer cells

Question 9

where does erythropoiesis mostly occur?

Answer 9

red bone marrow

Question 10

what organ mostly secretes erythropoietin? what is the effect of erythropoietin?

Answer 10

• kidneys

* promote the survival and proliferation of red blood cell progenitors in the red bone marrow

Question 11

describe the process of erythropoiesis, including the appearance of cells and how their structures change (4)

Answer 11

1 - pronormoblasts are the first recognisable red blood cell progenitors: large, basophilic cytoplasm (blue H&E)
2 - give rise to progressively smaller normoblasts: increased Hb, therefore stains progressively pinker
3 - reticulocytes are released into circulation: still able to synthesise Hb, but have lost their nucleus
4 - mature erythrocytes stain pink due to high levels of Hb

Question 12

what are human embryonic stem cells derived from? how are they obtained?

Answer 12

• derived from inner cell mass of blastocyst

* taken from embryos that was not suitable for implantation in IVF

Question 13

what are somatic stem cells?

Answer 13

undifferentiated stem cells found in the body used to replenish cell populations

Question 14

why are somatic stem cells not more widely used in medicine (at the moment)? (2)

Answer 14

• only a few in each tissue sample

* hard to maintain proliferation in culture

Question 15

what are induced pluripotent stem cells ?

Answer 15

somatic cells treated with transcription factors to switch on genes and increase the potency of the cell

Question 16

what characteristics of cancer and stem cells are present in cancer stem cells? (2)

Answer 16

• can self-renew and produce cells that differentiate

* can seed tumours when transplanted

Question 17

what are the 2 types of stem cell transplants used to treat some blood disorders (eg. leukaemia)?

Answer 17

• autologous - stem cells from patient (treated in lab before being returned)
• allogenic - from donor with same tissue type (HLA matched)