TOPIC I: Stem Cells

Question 1

what is their ability?

What are stem cells?

Answer 1

Stem cells are unspecialised cells.
Stem cells have the ability to divide into two identical cells, of which one remains unspecialised and the other one can undergo further division and differentiation to form specialised cells.
When unspecialised stem cells divide and develop to specialised cells, the process is called cell differentiation. Stem cells are common to all multi-cellular organisms.

Question 2

What are the features of stem cells?

Answer 2

1. They are unspecialised.
   SC does not have any tissue specific structures that allow it to perform specialised functions. Unspecialised stem cells can give rise to specialised cells like heart muscle cells, blood cells, or nerve cells which play specific roles.
2. They are capable of dividing and renewing themselves for long periods.
   Of the two daughter cells formed by mitosis of a stem cells, one cell remains unspecialised while the other differentiates.
3. They can give rise to specialised cell types.
   Internal signals are controlled by a cell’s genes while the external signals for cell differentiation include chemicals secreted by other cells, physical contact with neighbouring cells, and certain molecules in the microenvironment.

Question 3

What are the different types of potency a stem cell can have?

Answer 3

1. Totipotency (Zygotic stem cells)
   Diff into any cell type to form whole organisms and are also pluripotent and multipotent.
2. Pluripotent (Embryonic stem cells)
   Diff into almost any cell type to form any organ or cell type and so are not totipotent but are multipotent.
3. Multipotent (Myeloid and Lymphoid SC)
   Diff into a limited range of cell types of a closely related family of cells.
4. Unipotent
   One cell type, can self-renew

Question 4

What are embryonic SCs?
what do they give rise to?

Answer 4

ESCs obtained from the blastocyst are pluripotent, giving rise to all derivatives of the 3 primary germ layers, octoderm, endoderm and mesoderm.
These germ layers give rise to the multiple specialised cell types that make up the heart and other organs

Question 5

What are blood stem cells?

Answer 5

Maintain the steady state of functioning of tissues by replacing cells lost through disease, tissue injury or normal wear-and-tear.
Myeloid stem cells give rise to RBCs, platelets and white blood cells such as granulocytes.
Lymphoid stem cells give rise to WBCs such as B-lymphocytes, T-lymphocytes and killer cells.

Question 6

What are the moral dilemmas in using human ESCs?

Answer 6

(1) Prevent human suffering
(2) Respect of the value of human life.
To obtain ESCs, early human embryo has to be destroyed, this means destroying a potential human life. However, EScell research can also lead to new medical discoveries that may alleviate the suffering of many people.

Tampering With Nature
The use of hEScells or research and medical applications is often viewed as tampering with nature and hence going against the natural way of life.

Question 7

What is tampering with nature?

Answer 7

The use of hESCs for research and medical applications is often viewed as tampering with nature and going against the natural way of life.

Question 8

What are the features of IPSCs?

(Induced pluripotent stem cells)

Answer 8

Adult cells that have been genetically reprogrammed to ESC-like state by being forced to express genes and proteins that allows them to maintain the properties of ESCs.
Human IPSCs are able to express proteins that characterise them as SCs.
Self-renewing and pluripotent.

Question 9

What are the advantages of IPSCs?

Answer 9

Bioethics
Genetically matched cell lines
Easier to create
Used as a model of the study of diseases.

Question 10

How does a cell differentiate to form a specialised cell?

Answer 10

External or internal signals that trigger division and differentiation
By switching on or off the expression of certain genes;
different proteins are produced for the specialised cell to perform its specialised function.