Stem Cells

Question 1

type of stem cells

Answer 1

1. totipotent (zygotic)
   - dydx into all cell types that make up an entire organism including extraembryonic tissues like placenta
   - found in fertilised egg to 8 cell stage (zygotic SC)
2. pluripotent (embryonic)
   - dydx into all cell types that make up an organism except extraembryonic tissue
   - found in inner cell mass of blastocyst
3. multipotent (adult)
   - develop into a limited and related range of cell types and tissues
   - found in haematopoietic SC in bone marrow

Question 2

argument against using embryonic SC (HSBC)

Answer 2

1. some believe embryo has the status of human being as it has the potential to become one -> tantamount to murder
2. extracting SC from embryo to make replacement body cells is treating embryo as a source of spare parts
3. claims of benefits of SC research is overrated -> few examples of success in medical applications
4. possibility of unforeseen consequences in treated patient like possible risks of tumour formation, immunological reactions, unexpected behaviour of cells and unknown long term health effects

Question 3

argument for using embryonic SC

Answer 3

1. embryos are not equivalent to human life
2. some believe life only begins when a heartbeat develops or when the brain begins developing
3. can potentially treat a wide range of diseases as they have the potentially to grow indefinitely in a laboratory environment & can dydx into almost all types of bodily tissues
4. unethical not to use established protocols on ESC research to further research and help relieve human suffering

Question 4

advantages of using own injected SC instead of complete organ transfer [3]

Answer 4

1. will not cause immune system to be stimulated as there are no foreign cells -> no need to use immunosuppressants drugs
2. no need to source for suitable donor -> save time and money
3. SC are capable of cell proliferation and self-renewal -> required cells can grow in large quantity

Question 5

what are iPSC (induced pluripotent SC)?

Answer 5

1. pluripotent SC that are generated directly from adult somatic cells (non-pluripotent)
2. non-pluripotent cells can be induced to become pluripotent

Question 6

advantages of iPSCs [6]

Answer 6

1. does not generate and destroy any embryos
2. may enable an additional reproductive technology that generate sex cells -> treat infertility
3. generates pluripotent stem cell lines from patients with inherited diseases -> understand why disease develop & use in personalised drug discovery efforts
4. no need to use immunosuppressant drugs after transplant & overcome problem of looking for a suitable donor for transplantation
5. derived from patient’s own cells -> will not be rejected by immune system
6. adult tissue used to make iPSC can be easily obtained from donor without risk to donor

Question 7

possible problems of iPSC [3]

Answer 7

1. low efficiency -> conversion from adult somatic cells to iPSCs is incredibly low
2. genetic modification of adult somatic cells to obtain iPSCS may cause cancer by over expression of POG or switching off of TSG
3. ethical concerns related to creation of embryos & children from iPSC-derived sex cells

Question 8

what are ethical complications?

Answer 8

1. means of obtaining SC (techniques involving destruction of human embryos)
2. human cloning
3. exploitation of embryo & egg donors

Question 9

compare human embryonic SC & human adult SC [DRSAD]

Answer 9

[dy/dx ability]

[role in body]
1. ESC: develop embryo into an entire human
2. ASC: replace specific cells in body which die throughout life due to wear & tear, disease or illnesses

[sources]
1. ESC: unused IVF embryos that have been donated or embryos created for the purpose from donated eggs and sperms
2. ASC: bone marrow, muscles & skins, and from foetus, umbilical cord & placenta

[advantages in research & therapy development]
1. ESC: treat wide range of disease -> pluripotency allows SC to produce any cell type, strong ability to self-renew -> constant supply of ES cells, make up a significant proportion of developing embryo & easier to isolate and grow
2. ASC: less ethical considerations than ESC, avoid problem of immune rejection -> taken from patients’ own body -> cells are genetically identical

[disadvantages…]
1. ESC: genetically different to cells of potential patient -> immune rejection, ethical issues over embryo destruction
2. ASC: limited no. of diff. cell types, conditions support self-renewal have only been identified for a few tissue SC types (skin, cornea), found in small numbers & difficult to isolate, ASC w/ genetic mutation from patients’ own body will not be effective in treatment of genetic disorder

Question 10

Describe the characteristics to identify all S.C

Answer 10

1. Unspecialised cell types that do not have a specific structure or function
2. Able to self-renew via mitosis
3. Able to differentiate into specialised cell types

Question 11

Describe the characteristics to identify all S.C

Answer 11

1. Unspecialised cell types that do not have a specific structure or function
2. Able to self-renew via mitosis
3. Able to differentiate into specialised cell types