What is a stem cell What is a stem

| March 14, 2016

Question
1. What is a stem cell? What is a stem cell niche? Where are stem cell
niches found in vertebrates?
2. What are some signaling pathways that are found in stem cell niches?
3. How do niche cells regulate stem cells? Stem cells in niches are often found
attached to partner [non-stem cell] cells by adherens junctions. What is the
significance of this attachment?
4. What is the difference between totipotent, pluripotent, multipotent, and unipotent stem
cells?
5. Can stem cells be reprogrammed to form any cell type or tissue?
6. What four transcription factors can convert fibroblasts into induced pluripotent cells?
Why does the use
of one of these transcription factors cause a problem for later delivery of stem cells into
a patient?
7. How is cell fate established within pluripotent stem cells?
8. How does the cell cycle change as stem cells age?
9. How are embryonic stem cells kept in a pluripotent state?
10. What are satellite stem cells? What is myostatin and what role does it play during muscle
development?
11. Why do embryonic stem cells start to differentiate if they become too crowded in a petri
dish?
12. Do cloned animals age prematurely? Why might you think that they do?
13. What is nuclear transfer? How can you be sure that a cloned animal is derived from the
transferred
nucleus?
14. Why was the advent of induced pluripotent stem cells a breakthrough for regenerative
medicine?
15. What are two methods of manipulating embryonic stem cells or induced pluripotent stem
cells in
culture in order to cause them to differentiate into specific differentiated tissue types?
18. What are embryonic stem cells? Where are they found?
19.

Stem cells …
A. always divide asymmetrically to give rise to two different daughter cells.
B. are terminally differentiated.
C. can divide for the entire lifetime of the organism.
D. divide at a relatively fast rate.
E. All of the above.

20.
In some adenomas of the colon, intestinal crypt cells appear to have proliferated
abnormally to
form small tumors known as polyps. Studies on the familial type of such a disease led to the
identification
of a major signaling pathway (which was aberrant in the polyp cells) as being involved in
the

maintenance of the gut stem-cell compartment. What signaling pathway is this? Is it
upregulated or
downregulated in colon cancers?
A. MAPK pathway; up-regulated
B. MAPK pathway; down-regulated
C. Wnt pathway; up-regulated
1

D. Wnt pathway; down-regulated
E. Hedgehog pathway; down-regulated
21.
Indicate whether each of the following descriptions better applies to an asymmetric (A) or a
symmetric (S) stem-cell division strategy. Your answer would be a four-letter string composed of letters
A and S only, e.g. AAAA.
( ) It predicts the number of stem cells in a population to remain strictly constant after several
rounds of cell division.
( ) Cytoplasmic factors that control stemness are localized to one side of the cell before
cytokinesis.
( ) It is a more flexible strategy and can better accommodate the effect of environmental factors.
( ) It is more consistent with observations in gut stem cells and other stem cells.
22.
Which of the following statements is true regarding skeletal muscle development and
regeneration in humans?
A. Muscle is among those tissues that cannot be renewed once damaged.
B. Myoblasts are multipotent stem cells.
C. Muscle regeneration occurs as a result of stimulation of quiescent stem cells in the periphery
of muscle fibers.
D. A muscle that has been repaired once cannot be repaired again.
23.

All blood cells in our body …
A. have exceptionally short life-spans—at most a month or so.
B. are produced only before adulthood.
C. are ultimately generated from multipotent hematopoietic stem cells.
D. are made from progenitors that themselves circulate in the blood.
E. All of the above.

24.
Although quite inefficient, cloning by nuclear transplantation can be successful, as exemplified
by cloning of the famous Dolly. Such a success implies that …
A. nuclei can be reprogrammed by cytoplasmic factors in a foreign cytoplasm.
B. epigenetic changes in somatic cells are not functionally irreversible.
C. even a differentiated nucleus contains a complete genome, capable of supporting the
development of an entire organism.
D. All of the above.
25.
Cells of the inner cell mass in an early mammalian embryo can be isolated and grown in culture.
Which of the following is NOT true regarding these cells?
A. They are totipotent.
B. They can be introduced into another developing embryo where their progeny become
incorporated into the resulting adult animal, even into its germ line.
C. They are stem cells.
D. They can be manipulated in culture to give rise to almost any type of differentiated cell.
26.
Which group of factors is thought to impede iPS cell generation from a differentiated cell,
inasmuch as the reprogramming efficiency is increased when the activity of the factors is decreased?
A. Histone acetyl transferases
B. Histone deacetylases
C. Chromatin remodelers
D. DNA demethylases
E. All of the above

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