stem cells Flashcards
What is a stem cell?
- A stem cell is a cell that can divide and differentiate
- Once cells differentiate, they specialise
Why do stem cells self-renew AND differentiate?
Self renewal - maintains the stem cell pool
Differentiation - replaces dead or damaged cells throughout your life
Differentiated Cells [4]
- All cells contain the entire genome for that organism but only certain genes are expressed in any one cell at any one time
- Some genes are permanently expressed in all cells e.g. the genes that code for enzymes involved in respiration
- Some are permanently switched off, while others are switched on only when needed
- Differentiated cells differ from each other as they produce different proteins
Types of Stem Cells [4]
- Totipotent
- Pluripotent
- Multipotent
- Unipotent
Totipotent Stem Cells [3]
- Found in the zygote
- Is the first cells that a fertilised egg divides into
- Can divide into any type of cell
Pluripotent Stem Cells [2]
- Are embryo cells
- Can differentiate into almost any cell (except placental)
Multipotent Stem Cells [2]
- Are adult stem cells (but not just in adults)
- Can differentiate into a limited number of cells (bone marrow stem cells + any blood cell)
Unipotent Stem Cells [2]
- Only differentiate into one type of cell (e.g. skin cells)
- It is debated whether they truly exist
Where are they found… [4]
Embryonic stem cells - pluripotent
Placental stem cells - probably multi, maybe pluripotent
Umbilical cord blood stem cells - multipotent
Adult stem cells - multipotent
Pluripotent (Embryonic) Cells [5]
- Are found inside a blastocyst
- Embryonic stem cells are taken from the inner cell mass
- They are cultured in the lab in a fluid with nutrients to grow more cells
- They may differentiate into all possible types of specialized cells (except placental cells)
- Depending upon the conditions they are grown under
What is the difference between pluripotent and multipotent stem cells? [2]
- Pluripotent are embryo stem cells that can differentiate into almost any type of cell
- Multipotent are adult stem cells and can only divide into the cells in the tissue they are associated with
Induced Pluripotent Stem Cells (iPS cells) [3]
- SHINYA YAMANAKA
- Unipotent cells are induced to become pluripotent stem cells
- Certain genetic factors are altered
- Then different genes and transcriptional factors are expressed to allow these cells to differentiate
Give 4 Possible Uses of Pluripotent Stem Cells [4]
- Parkinson’s disease, Alzheimer’s disease, spinal cord damage
- Heart tissue after heart attacks
- Type I diabetes
- Organs for transplant (no rejection issues, no waiting lists)
Places to obtain Stem Cells [4]
- Spare embryos created during IVF: Those that aren’t implanted can have stem cells removed from the inner blastocyst
- Cell removed for pre-implantation genetic diagnosis at the 8 cell stage of an embryo: The embryo can still develop normally and the cell can be cultured to produce stem cells
- Umbilical cord blood: Contains pluripotent cells that can be cultured
- Adult stem cells: found in the brain, liver, skin, bone marrow etc. There are very few and they can be difficult to harvest, but some are already used to treat cancers
How are Stem Cells produced from Embryos? [5]
- Spare embryos from IVF are cultured to the blastocyst
stage - The stem cells are removed and the embryo discarded
- The stem cells are used in research to see if tissues for transplant could be created
- If the right type of tissue is developed, there may still be issues with rejection by the body
- This may be overcome by tissue typing or use of drugs to avoid rejection
