[20.2] stem cells and totipotency Flashcards
what is the importance of all cells containing all genes?
- cells of multicellular organisms are adapted in different ways to perform a particular role
- all cells in an organism are derived from mitotic divisions of the zygote so they must contain exactly the same genes
- every cell is therefore capable of producing everything the body can make
- only certain genes are expressed in any one cell at any one time
- some genes are permanently switched on whilst others are not
what are totipotent cells?
cells, such as fertilised eggs, which can mature into any body cell
what happens to totipotent cells later?
- they differentiate and become specialised for a specific function
- during the process of cell specialisation only some of the genes are expressed so only part of the DNA of a cell is translated into proteins
how can genes be prevented from expressing themselves?
- preventing transcription so preventing the production of mRNA
- preventing translation
what are stem cells?
undifferentiated dividing cells that occur in animal tissues which need to constantly be replaced
what is self-renewal?
the process by which stem cells form identical copies of themselves
what are 4 sources where stem cells originate in mammals?
- embryonic stem cells
- umbilical cord blood stem cells
- placental stem cells
- adult stem cells
describe embyronic stem cells
- come from embryos in the early stages of development
- can different into any type of cell in the initial stages of development
describe umbilical cord blood stem cells
- derived from umbilical cord stem cells
- similar to adult stem cells
describe placental stem cells
- found in the placenta
- develop into specific types of cells
describe adult stem cells
- found in body tissues of the fetus through to the adult
- specific to a particular tissue or organ where they produce the cells to maintain and repair tissues throughout an organism’s life
what are the 4 types of stem cells?
- totipotent stem cells
- pluripotent stem cells
- multipotent stem cells
- unipotent stem cells
describe totipotent stem cells
- found in the early embryo
- can differentiate into any type of cell
how is a zygote totipotent?
- all cells are formed from a zygote
- as the zygote divides and matures, its cells develop into more specialised pluripotent stem cells
describe pluripotent stem cells
- found in embryos
- can differentiate into almost any type of cell
- include embyronic stem cells, fetal stem cells etc.
describe multipotent stem cells
- found in adults
- can different into a limited number of specialised cells
- usually develop into particular cells eg. stem cells in bone marrow can produce any type of blood cell
- eg. adult stem cells, umbilical cord blood cells
describe unipotent blood cells
- can only differentiate into a single type of cell
- derived from multipotent stem cells
- made in adult tissue
- eg. cardiomyocytes, heart muscle cells that divide to produce new heart tissue
how are induced pluripotent stem cells produced? (iPS cells)
- type of pluripotent cell produced from unipotent stem cells
- body cells are genetically altered in a lab to make them acquire more characteristics of embryonic stem cells
- induce genes and transcriptional factors ie. turn on genes that are otherwise turned off
how are iPS cells better than embryonic stem cells?
- capable of self-renewal
- using them in medical research and treatment overcomes many of the ethical issues surrounding the use of embryos in stem cell research
how can pluripotent cells be used to treat human disorders? (9)
- heart muscle cells - heart damage eg. due to heart attack
- skeletal muscle cells - muscular dystrophy
- β cells of pancreas - type 1 diabetes
- nerve cells - parkinson’s, MS, strokes, alzheimer’s, paralysis
- blood cells - leukaemia, inherited blood disorders
- skin cells - burns and wounds
- bone cells - osteoporosis
- cartilage cells - osteoarthiritis
- retina cells of the eye - macular degeneration
