Stem cells Flashcards
Stem cells
Cells that can develop and specialise into other types of cell (a process called differentiation)
And replace themselves indefinitely by cell division
Differentiation
Ability of stem cells to divide and specialise into any kind of cell
How does cell differentiation occurs
Control of gene expression: cell will only transcribe/translate specific genes in DNA that produce specific polypeptides so the cell can carry out its specific functiom
How is the potency of stem cells measured?
Based on how many cells they can divide and specialise into
Hierarchy of stem cell potency
Totipotent stem cells
Pluripotent stem cells
Multipotent stem cells
Unipotent stem cells
Totipotent cells
Can differentiate and specialise into any type of body cell
When are totipotent stem cells present?
Only in the very early stages of embryo development
Never as adults
Pluripotent stem cells
Can specialise into most types of body cell BUT NOT ALL
When are pluripotent stem cells present?
Later stages of embryo development
Never as adults
Adult stem cells include?
Multipotent stem cells
Unipotent stem cells
Multipotent stem cells
Can only specialise into a couple body cell types
Unipotent stem cells
Can only specialise into 1 type of body cell
Do mature humans have stem cells?
Yes, but adult stem cells such as multipotent or unipotent ones
Example of a unipotent stem cell
Stem cell called cardiomyoblasts that can ONLY specialise into cardiomyocytes
How can stem cells be used in treatment?
Induced pluripotent stem cells
What are iPS cells?
Induced pluripotent stem cells
Made up of adult body cells that were induced back to the pluripotent stem cell stage
How are iPS cells made?
Adult body cell with same DNA as patient
Introduction of transcription factors that inhibit/stimulate transcription of specific base sequences in DNA to mRNA so specific polypeptides arent translated, and specific polypeptides are translated= pluripotent stem cell state
Advantages of iPS cells?
More ethical because not taken from embryo stage, no ‘future life killed’
iPS cell is genetically identical to donor’s DNA so no rejection to foreign tissue
Disadvantage of stem cell treatment
Have ability to divide indefinitely so transplanted cells may undergo uncontrolled division to produce a tumour
