20.2: Stem cells and totipotency Flashcards
Cell differentiation
The process by which each cell develops into a specialised structure suited to the role that it’ll carry out.
All cells in an organism…
contain exactly the same genes
Some genes are permanently…
expressed in all cells
Totipotent cells
Can mature into any type of body cell
Example of totipotent cells
fertilised egg
How are genes prevented from being expressed?
2
preventing transcription so the production of mRNA
preventing translation
Stem cells
Unspecialised cells that can develop into other types of cells
How do stem cells become specialised?
Divide into new cells which then become specialised
Where are stem cells found?
2
in the embryo (in early stages of development)
some adult tissues
Stem cells link to totipotent cells
stem cells that can mature into any type of body cell are totipotent cells
Self-renewal
Stem cells ability to divide and form an identical copy of themselves
Sources from which stem cells originate from
4
embryonic stem cells
umbilical cord blood stem cells
placental stem cells
adult stem cells
Types of stem cells
4
totipotent
pluripotent
multipotent
unipotent
Pluripotent stem cells
(As the zygote matures in develops into slightly more specialised cells)
- Can still specialise into any cell in the body, but lose the ability to become the cells that make up the placenta.
Multipotent stem cells
Are able to differentiate into a few different types of cells and are found in adults.
Unipotent stem cells
Can only differentiate into a one type of cell and are derived from multipotent cells and made in adult tissue.
Induced pluripotent stem cells
(iPS cells)
Type of pluripotent cell that is produced from unipotent stem cells which are genetically altered so they can acquire the characteristics of embryonic stem cells.
Genes are induced meaning
turning on genes that are turned off
Induced pluripotent stem cells are capable of
self-renewal
Induced pluripotent stem cells advantage
could replace embryonic stem cells in medical research and overcome ethical issues
Example of use of pluripotent cells in treating human disorders
regrow tissues that have been damaged
