Most of a cell’s DNA is not translated

Question 1

what are stem cells

Answer 1

Unspecialised cells capable of:
* Self-renewal; can divide to replace themselves
* Specialisation/differentiation; can develop into other types of cell

Question 2

what is stem cell specialisation

Answer 2

1. Stimulus e.g. chemical
2. Causes selective activation of genes – some genes activated while others inactivated
   * E.g. muscle cells genes coding for actin and myosin need to be activated
3. mRNA only transcribed from active genes → translated on ribosomes = proteins
4. These proteins modify cell permanently and determine cell structure / function

Question 3

what are the types of stem cells

Answer 3

• Totipotent cells
• Occur for a limited time in early mammalian embryos
• Can divide and differentiate into every cell type in body (including the cells that
  support the embryo, such as the placenta)
• Pluripotent cells
• Found in embryos
• Can divide and differentiate into most cell types (every cell type in body but not
  the cells of the placenta)
• Multipotent cells
• Found in mature mammals
• Can divide and differentiate into a limited number of cell types
• E.g. multipotent cells in bone marrow can differentiate into different types of
  blood cell
• Unipotent cells
• Found in mature mammals
• Can divide and differentiate into just one cell type
• Example: cardiomyocytes (cardiac muscle cells) can be made from unipotent
  stem cells

Question 4

how are stem cells used in medicine

Answer 4

• Regrow damaged tissues in accidents (i.e. skin grafts) or by disease (i.e. neurodegenerative diseases, Parkinson’s disease)
• Lots of potential links to topic 6 here e.g. B cells of the pancreas in type 1 diabetes
• Drug testing – used to grow artificial tissues
• Developmental biology research – provide insight into embryological development

Question 5

what are Induced pluripotent stem cells

Answer 5

• How they are produced
  1. Produced from adult somatic cells (non-pluripotent cells or fibroblasts)
  2. Specific protein transcription factors associated with pluripotency put into cells,
  causing the cell to express genes associated with pluripotency (reprogrammed)
  3. Cells cultured
  4. = Induced pluripotent stem cells
• Used in medical treatment instead of embryonic cells…
  ✓ No immune rejection as can be made using patient’s own cells
  ✓ Overcome some ethical issues with using embryonic stem cells e.g. no
  destruction of embryo and adult can give permission

Question 6

Evaluate use of stem cells in treating human disorders

Answer 6

For:
* Use of embryonic stem cells
* Tiny ball of cells, incapable of feeling pain, not equivalent to a human
* Would otherwise be destroyed (if from infertility treatment which creates more
than needed)
* Duty to apply knowledge to relieve human suffering
Against:
* Use of embryonic stem cells
* Embryo is a potential human; should be given rights
* Scientific
* Induced pluripotent stem cells – cannot yet reliably reprogramme stem cells
* Could begin to multiply out of control, and cause tumours