stem cells Flashcards
(24 cards)
why are stem cells unique cells?
list 3 reasons
- undifferentiated and unspecialised
- undergo extensive proliferation and self-renewal
- able to differentiate to produce specialised cells, upon receiving appropriate molecular signals
3 functions of stem cells
self-renewal to ensure constant pool of stem cells
growth and development
differentiate into specialised cells to regenerate/replace cells lost from cell death and injury
What are the possible types of cell division applicable to stem cells?
symmetrical and asymmetrical division
symmetrical division of stem cells
(2 steps)
produce 2 identical daughter stem cells to ensure constant pool of stem cells for further division
asymmeterical division of stem cells
stimulated by molecular signals
produces 1 daughter, to ensure constant pool of stem cells, and 1 progenitor, to replace a population of specialised cells in specific dead tissue
examples of molecular signals
transcription factors, growth factors, hormones etc
types of stem cells
totipotent, pluripotent, multipotent
what is totipotent stem cell?
(hint: largest group)
ability to differentiate into all of the cell types that make up an organism INCLUDING extraembryonic tissue (placenta)
example and sources of totipotent
zygotic stem cell from fertilised egg to 8 cell stage
DAYS 1-4
what is pluripotent stem cell?
(hint: 2nd largest)
ability to differentiate into all EXCEPT extraembryonic tissue (placenta)
CANNOT form entire organism
example and sources
embryonic stem cells derived from cells of inner cell mass of blastocyst
DAY5
whats multipotent stem cell?
(hint: smallest)
ability to differentiate into several related cell types but far fewer types than others
examples and sources of multipotent
Adult stem cells
a. blood/haematopoietic stem cells found in BONE MARROW, only differentiates into diff blood cells
b. neural stem cells differentiate into nerve cells and glial cells
c. lymphoid stem cells give rise to b and t lymphocytes
d. myeloid stem cells give red blood cells and macrophages
parts of blastocyst
trophoblast (outer layer, develops into placenta and supporting tissues)
inner cell mass (pluripotent, develops into foetus)
blastocyst cavity (fluid and chemicals for cellular differentiation)
adult stem cells
embryonic stem cells proliferate and differentiate into adult stem cells (multipotent)
produce specialised cells for growth and development and regeneration of cells lost due to cell death and injury
why do different stem cells have different differentiation potential?
molecular signals received by receptors on cells lead to signal transduction and gene expression, with only certain genes expressed/repressed through acetylation and methylation
why can stem cells continue to self renew and proliferate without apoptosis?
telomerase gene is expressed and prooduces telomerase reverse transcriptase (TERT), extending telomere length
–> indefinite cell division without apoptosis
principles of bioethics (3)
- respect for persons/autonomy
- maximise benefits, minimise harms
- justice
against using stem cells (3 reasons)
- embryo has status of human being, hence murder
- embryo is just used as spare parts
- current benign uses may lead to abuse in the future
for using stem cells (3 reasons)
- not equivalent to human life (not conscious, cannot feel, cannot survive)
- surplus embryos in ivf are destoryed, can be used for research instead
- treats a wide range of diseases and potential to grow indefinitely
solution to overcome
induced pluripotent stem cells
iPS cells
pluripotent stem cells generated directly from adult somatic cells
HOW: introducing 4 specific genes encoding for transcription factors, lost specialised functions
advantages of iPSCs
- does not create or destroy human embryos
- derived from patient’s own cells, no rejection by immune system
- no need for immunosuppressant drugs
possible problems of iPSCs
- low efficiency
- reprogramming can introduce genetic modifications that may cause cancer
