stim kells

Question 1

What are stem cells

Answer 1

undifferentiated cells, capable of long term self renewal (through cell division) and can divide without limit

Question 2

What happens to potency as stem cells differentiate

Answer 2

progressive restriction of developmental potential/loss of potency

Question 3

Describe the different stem cells

Answer 3

totipotent, pluripotent, multipotent, unipotent

Question 4

What do stem cells form when they divide

Answer 4

1) produces transient amplifying cell and also another stem cell
2) Or two populations of stem cells, one population reproduces itself as stem cells, other

Question 5

True of false, more division occurs through TAC not stem cells

Answer 5

True

Question 6

Why are adult stem cells important

Answer 6

• Important to maintain cell populations that last for long periods of time and must be renewed
• They generate the cell types of the tissue in which they reside
• Important for continued production of cells in: epithelium, blood, muscle, liver and brain

Question 7

Describe totipotent stem cells

Answer 7

cells from early mammalian embryo. Can form entire blastocyst (embryonic tissue and fetal placenta around it)

Question 8

Pluripotent stem cells…

Answer 8

: can form embryo but not surrounding placental tissue. Give rise to 3 germ layers (ectoderm, endoderm, mesoderm)

Question 9

Multipotent stem cells ..

Answer 9

can give rise to many cell types

Question 10

Unipotent stem cells/commited stem cell…

Answer 10

Give rise to one cell type

Question 11

Describe journey of embryonic stem cell

Answer 11

• In the 3-5 day embryo (blastocyst)
• Inner stem cell give rise to entire body
• ESC include pluripotent and totipotent stem cells
• Totipotent from blastocyst cells at 2 or 4 cell stage. I.e. can obtain complete blastocyst from cells at this stage (i.e. embryo+fetal placenta aka trophoblast)
• Pluripotent – at 8 cell stage (but cells can’t generate complete blastocyst)

Question 12

What are iPS cells

Answer 12

arise from adult specialised cells that have been reprogrammed genetixally to be like stem cells
• Using genetically manipulation (viral transfection/ using viral vectors) expression of 4 genes is sufficient to convert adult skin fibroblast into iPSCs.

Question 13

How can iPS cells be used

Answer 13

• They can differentiate into desired cell types for in vitro models of disease (espeiclaly inaccessible cells like neurones) and could be used in stem cell transplantation therapy of “self” cells

Question 14

Describe journey of stem cells in epithelium of gut

Answer 14

Stem cells at the base of layer and renew epithelium. Stem cells migrate upwards and as they do they differentiate towards the lumen
Basal cell layer contain few stem cells, mainly Transient amplifying cells. These have reduced diff capacity and make many terminally differentiated cells.

Question 15

Why is base of epithelium dark when stained

Answer 15

dense staining as lots of nuclei present as lots of cells undergoing lots of cell division (stem cells).

Question 16

How do diff cells take on specific identities

Answer 16

• Selective gene expression: terminally differentiated cells express types express specific proteins (e.g. Hb in erythrocytes)

Question 17

How is diff sequential process

Answer 17

developmental potential of cells become progressively restricted as they become more specialised. Cells start to differentiate before they exit cell cycle during G1 and enter G0 and thus terminal differentiation. Most cell types stay terminally differentiated (can’t re-enter cell cycle + differentiate again),

Question 18

Why are hepatocytes unique

Answer 18

can dedifferentiate and re-enter cell cycle to make new hepatocytes to rebuild liver

Question 19

Is genome affected by differentiation

Answer 19

• Genome of differentiated cells not normally altered in sequence

Question 20

What factors maintain and produce diff state

Answer 20

• Transcription factors and chromatin modification specify and maintain differentiated state

Question 21

How can TF and chromatin modification affect how cells diff

Answer 21

. TF that drive differentiation block cell cycle, methylation of promoters of inactive genes and deacetylation of associated histones means resulting chromatin is stably inactivated (heterochromatic) whereas active genes are stably activated by opposite mechanisms (chromatin is euchromatic). This stabilises differentiated state of cell,(by stabilising genes in inactivated/off state)

Question 22

Apart from TF and chromatin modification, how can differential gene expression be regulated

Answer 22

• alternate splicing,
• RNA editing
• genomic rearrangements.

Question 23

How can alternate splicing lead to differential gene expression

Answer 23

specific gene has the ability to splice RNA with varying exons to make different proteins. Make cells different, using same gene but slicing RNA

Question 24

True of false: Pluripotent cells have specialised gene expression programmes but can still proliferate to different cell types

Answer 24

True

Question 25

How can cells be reprogrammed to become mesoderm

Answer 25

 Take ectoderm layer and transplant onto endoderm, Cells reprogrammed to become mesoderm by being in contact with underlying endoderm

Question 26

Describe how cells have plastic state

Answer 26

cells don’t know what they will become and change differentiation pathway based on contact with other cells.

Question 27

What is meant by juxtracrine signalling

Answer 27

Contact dependent signalling

Question 28

How is cell type specific transcription achieved -

Answer 28

Diffusible ligand binds to cell surface receptor/intracellular receptor (paracrine)

• Cell surface ligand and receptor of adjacent cells interact – juxtracrine (contact dependent signalling)
• Gap junctions – juxtracrine