Stem Cells

Question 1

define stem cells

Answer 1

unspecialised cell from the embryo, fetus, or adult

Question 1

define stem cells

Answer 1

unspecialised cell from the embryo, fetus, or adult

Question 2

what are the key characteristics of all stem cells?

Answer 2

• long-term self-renewal via mitosis
• has the ability to differentiate to give rise to specialised cells

(large nuclear to cytoplasmic ratio)

Question 3

what does stem cell potency refer to?

Answer 3

• the range of cell types to which a stem cell can give rise to
• number of possible developmental pathways
• differential potential

Question 4

state the three types of stem cell potency, and the descendent sequence

Answer 4

totipotent to pluripotent to multipotent

Question 5

define totipotent stem cells, and where are they found?

Answer 5

can differentiate to give rise all cell types that make up an organism
- zygotic stem cell (first few cells of the fertilised zygote)

Question 6

define pluripotent stem cells, and where are they found?

Answer 6

give rise to three germ layers (mesoderm, endoderm, ectoderm; everything except extra-embryonic membranes)

• embryonic stem cells (early embryos)
• from inner cell mass of blastocyst

Question 7

define multipotent stem cells, and where are they found?

Answer 7

differentiate into limited number of cell types: many cell lines within a specific tissue type
- adult stem cells (eg. blood, lymphoid, myeloid)

Question 8

what are committed cells?

Answer 8

• more limited pathway of development compared to pluripotent
• destined to produce specific group of cells

Question 9

what is a precursor or progenitor cell?

Answer 9

partly differentiated cells that give rise to differentiated cells (committed)

Question 10

what are the two types of mitotic division in stem cells?

Answer 10

• symmetric: 2 genetically identical stem
• asymmetric: 1 stem, 1 committed progenitor

Question 11

what is the importance of asymmetric mitotic division?

Answer 11

1. preserves population of undifferentiated stem cells
2. steadily produces stream of differentiated cells

Question 12

what are the sources of embryonic stem cells in humans?

Answer 12

1. inner cell mass of blastocyst (when zygote is implanted)

Question 13

what are six defining properties of an embryonic stem cell?

Answer 13

1. can undergo long-term mitotic self-renewal without differentiation
2. maintains stable, diploid, normal chromosome complement
3. can give rise to three germ layers (ecto, endo, meso)
4. can develop into all fetal tissues
5. clonogenic (makes genetically identical cells)
6. easy to get pure and mass-cultivate

Question 14

what are the two primary roles of adult / somatic stem cells?

Answer 14

1. maintain / repair tissues
2. replace injured or diseased cells

Question 15

what are four defining properties of an adult stem cell?

Answer 15

• long-term mitotic self-renewal
• can give rise to fully-differentiated cells
• clonogenic
• full chromosome complement

Question 16

what are the three lineages in hematopoiesis?

Answer 16

1. lymphoid: produces B + T lymphocytes
2. myeloid: rest of WBCs (eg. monocytes, mast, leukocytes)
3. erythroid: red blood cells / erythrocytes

Question 17

what are the four principles of bioethics?

Answer 17

1. respect for persons
2. maximising benefits, minimising harms
3. justice
4. care

Question 18

what are the arguments for and against therapeutic cloning?

Answer 18

for:
- huge benefits outweigh wrong-doing

against:
- devalue human life