Stem Cells and Totipotency Flashcards
What’s cell differentiation
The process by which each cell develops into a specialised structure suited to the role that it will carry out
Why is it that all cells contain the same gene but for example why does all intestine produce maltase rather then insulin and B cells of the pancreas produce insulin rather then maltose
Although all cells contain all genes, only certain genes are expressed (switched on) in any one cell at any one time
Which genes are permanently switched on and which are off
That code for essential chemicals such as enzymes Involved in respiration
Those coding for enzymes and other proteins in essential processes like transcription, translation
Not on would be the gene for insulin in cells lining the small intestine
What are the proteins that a cell produced are coded by?
Genes it posses or more accurately the genes that are expressed
What are Cells such as fertilised eggs, which can mature into any body cell called
Totipotent cells
Why is only part of the dna of a cell translated into proteins
As during the process of cell specialisation only some of the genes are expressed
The cell therefore only makes proteins that it requires to carry out its specialised function
How are genes prevented from expressing themselves
Preventing transcription and so preventing the production of mRNA
Preventing translation
Why can’t specialised cells develop into other cells
As specialisation is irreversible in most animal cells, once cells have matured and specialised they can no longer develop into other cells
In mature mammals only a few cells regain the ability to differentiate into other cells
What are stem cells
Undifferentiated dividing cells that occur in adult animal tissues and constantly need to be replaced
Where do stem cells originate from in mammals
Embryonic stem cells - come from embryos in early stages of development. They can differentiate I go any type of cell in the initial stages of development
Umbilical cord blood stem cells - are derived from umbilical cord blood and are similar to adult stem cells
Placental stem cells- found in the placenta and develop into specific types of cells
Adult stem cells - found in the tissue of the fetus through to the adult. Specific to a particular tissue or organ within which they produce the cells to maintain and repair tissues throughout an organisms life
What are totipotent cells
Found in the early embryo and can differentiate into any type of cell.
Since all body cells are formed from a zygote, it follow that the zygote is totipotent. As the zygote divides and matures, it’s cell develops into slightly more specialised cells called pluripotent stem cells
What are pluripotent cells
Found in embryos and can differentiate into almost any type of cell
What are multipotent stem cells
Found in adults and can differentiate into a limited number of specialised cells. They usually develop into cells of a particular type
Examples are adult stem cells and umbilical cord blood stem cells
What are unipotent stem cells
Can only differentiate into a single type of cell. They are derived from multi potent cells and are made in adult tissue
What are induced pluripotent stem cells
Type of pluripotent cell that is produced from unipotent stem cells. Unipotent cell may be almost any body cell
What happens to the body cells to make them into a type of pluripotent cell
They are genetically altered in a lab to make them acquire the characteristics of embryonic stem cells
How do we make the unipotent cells acquire the new characters
It involves inducing genes and transcriptional factors within the cell to express themselves
iPS are self renewal what does this mean
They can potentially divide indefinitely to provide a limitless supply.
As such they could replace embryonic stem cells in medical research and treatment and so overdone many ethical issues in using embryos in stem cell research
What can pluripotent cells used to do in treating human disorders
Used to regrow tissues that have been damaged in some way either by accident or as a result of disease
Suggest a reason why skin cells restrain an ability to divide by being unipotent when the cells of some other organs do not
Skin cells, being on the outside of the body, are subjected to wear and tear and so need replacing frequently. Many other organs are less prone to damage and need little cell replacement
