Stem Cells

Question 1

how using human induced pluripotent stem cells (ipscs) in medical treatments avoid ethical problems of using other pluripotent stem cells

Answer 1

• avoids exploitation of pluripotent stem cells from blastocyst
• no destruction of human embryos nor denial to the right of life
• no ethical problem on treatment of unused embryos
• no exploitation of women such as lowering of her future fertility from the extraction procedures involved in ova donation

Question 2

features of stem cells

Answer 2

• unspecialised (no tissue-specific structures, no specialised function)
• capable of self-renewal by mitosis for long-term
  able to give rise to specialised cell types

Question 3

totipotent stem cell

Answer 3

zygotic stem cells

Question 4

pluripotent stem cells

Answer 4

embryonic stem cells

Question 5

multipotent stem cells

Answer 5

blood stem cells (myeloid and lymphoid stem cells)

Question 6

define totipotent

Answer 6

• daughter cells can differentiate into any cell types to form whole organisms
• are pluripotent and multipotent

Question 7

define pluripotent

Answer 7

• daughter cells can differentiate into almost any cell type to form any organ or type of cell except extra-embryonic layer
• not totipotent but are multipotent

Question 8

define multipotent

Answer 8

• daughter cells can differentiate into a limited range of cell types
• not totipotent or pluripotent

Question 9

functions of embryonic stem cells

Answer 9

• ES cells obtained from blastocyst are pluripotent
• give rise to all three derivatives of the three primary germ layers : ectoderm, endoderm and mesoderm during development
• these germ layers give rise to multiple specialised cell types

Question 10

functions of blood stem cells (aka adult stem cells)

Answer 10

• multipotent
• have the ability to differentiate into limited range of cell types, usually of a closely related family of cells
• myeloid stem cells give rise to RBCs, platelets and WBCs such as granulocytes
• lymphoid stem cells give rise to WBCs such as B lymphocytes , T lymphocytes and natural killer cells
• primary function is to maintain the steady state functioning of tissues by replacing cells lost through disease, tissue injury or normal wear-and-tear

Question 11

ethical aspects of gene editing

Answer 11

• no embryonic stem cells used = no embryos destroyed = does not involve taking away a potential life
• viewed as tampering with nature and going against the natural way of life
• patients need to be informed of potential risks and failures
• may be exploited by humans to select for favourable traits

Question 12

why stem cells suitable for treating genetic diseases

Answer 12

• stem cells capable of dividing by mitosis and renewing themselves for long periods of time
• permanent cure
• give rise to ‘healthy’ specialised cell types which are normal via further division and differentiation
• maintain the steady state of functioning of tissue by generating replacement for cells lost through disease

Question 13

how stem cells can continue to divide mitotically, whilst other cells can only do this for a set number of division

Answer 13

• stem cells contain telomerases which extend the telomeres at the ends of the chromosomes
• can undergo long term mitotic cell division
• other cells do not have telomeres, subjected to end replication problem
• once telomeres are shortened to a critical length, signal cell to stop cell division, and initiate apoptosis