Stem Cells

Question 1

Describe the 3 characteristics of a stem cell

Answer 1

1) unspecialised cell that can
2) divide and self-renew indefinitely
3) has the ability to differentiate into specialised cells under appropriate conditions

Question 2

How are stem cells unspecialised

Answer 2

absence of tissue-specific structures that allow it to perform specialised
functions.

Question 3

How can continually divide and self-renew for a long period of time

Answer 3

1. Stem cells are able to proliferate unlike other cells
   Can be symmetrical stem symmetrical differentiated or asymmetrical
   ➢ two daughter cells that remain as stem cells, or
   ➢ two daughter cells that are committed to differentiate into a specialised cell.

A stem cell can divide -> 1 daughter cell
remains as a stem cell + 1 daughter cell differentiate into a
specialised cell.

Question 4

How do SCs have ability to differentiate into specialised cell types under appropriate conditions,

Answer 4

1) intracellular signals:
❖ Cytoplasmic factors (proteins) encoded by genes in the genome of the cell. These factors send signals to the nucleus via transcription factors to turn on and off various genes.

2. extracellular signals:
   ❖ Chemical molecules/growth factors surrounding a cell, which may be secreted by neighbouring cells.
   ❖ Physical contact with neighbouring cells.

Question 6

Describe totipotent + eg.

Answer 6

ability to differentiate into any cell type in the adult body,
+ cells of the extraembryonic membranes
-> can develop into whole organism
(Zygotic stem cells)

Question 7

Describe pluripotent + eg.

Answer 7

ability to differentiate into all cell types in the adult body, but
not cells of the extraembryonic membranes.
eg. embryonic cells in inner cell mass (blastocyst)
haematopoietic stem cells

Question 8

Describe multipotent + eg.

Answer 8

ability to differentiate into a limited range of cell types.