Stem Cells

Question 1

Stem cell characteristics

Answer 1

Undifferentiated or partially differentiated
Generally slow dividing, but can divide indefinitely (telomerase- prevents ends of chromosomes, telomeres, from getting shorter with each division)
Express different genes than the cells that they will make

Question 2

Stem cell division

Answer 2

Divide to generate themselves

Divide to differentiate

Question 3

Signals that prompt differentiation

Answer 3

Hormones
Loss of attachment to extracellular matrix
Force/stretching

Question 4

Stem cells in gut

Answer 4

Stem cells in crypt (cavities in-between villi) replace worn out or sloughed off cells in villi

Question 5

Wnt signaling

Answer 5

Wnt binds to receptor -> activates signaling protein -> inactivates APC (tumor supressor)-containing complex -> stable beta-catenin (signal) -> active TCF complex -> transcription of Wnt-responsive genes leading to proliferation of gut stem cells
Without Wnt: APC-containing complex is active -> degrades beta-catenin -> TCF complex is inactive -> Wnt-responsive genes are off

Question 6

Stem cells in skin

Answer 6

Cells near basal lamina replace cells that are lost at the surface of the skin

Question 7

Cells that hemopoietic stem cells in bone marrow can make

Answer 7

Lymphocyte stem cells: T lymphocyte (thymus) and B lymphocyte (bone marrow)
Myeloid stem cells: eosinophil, basophil, neutrophil, monocyte, megakaryocyte, red blood cell

Question 8

Multipotent stem cells

Answer 8

Can make a few different types of cells (ex- hemopoietic stem cells)
Found in adults

Question 9

Pluripotent stem cells

Answer 9

Can make any cell in your body: unrestricted development potential
Found in adults (ex-bone marrow), but usually in embryonic stem cells

Question 10

Totipotent stem cells

Answer 10

Can make any cell in your body as well as extra-embryonic tissues (placenta, etc.)
Found in embryonic stem cells

Question 11

Veg F

Answer 11

Signal that causes stem cells to develop into endothelial cells (blood vessels)

Question 12

Obtaining embryonic stem cells

Answer 12

Cells are taken from early embryo (blastocyst) and then cultured
ESCs are given signals to develop into different cell types (fat cells, neurons, macrophages, smooth muscle cells, glial cells, etc.)

Question 13

Neurotrophin

Answer 13

Signal that causes stem cell to develop into neuron

Question 14

Pros and cons to stem cells

Answer 14

Pros: can make anything with right chemical cues, could be cloned with your DNA to make host-specific tissue, replacement of damaged tissue
Con: potential for rejection of not your own DNA, potential for tumor formation, ethical and legal issues, work with human ESCs is in its infancy

Question 15

Obtaining and using ESCs

Answer 15

Unfertilized egg from an adult female: DNA is removed
Egg is fused with adult cells containing genome to be cloned
Cell divides and forms early embryo
Reproductive cloning: embryo placed in foster mother
Therapeutic cloning: cells transferred from early embryo to culture dish

Question 16

Inducible pluripotent stem cells

Answer 16

Differentiated cells stably transfected with certain genes revert to an ESC-like state
Genes include one that induces cell growth and several transcription factors found active in ESCs
May present a way around the ethical dilemma
To form: take fibroblast from adult skin biopsy and give it the 3 key genes to create stem cell