Stem Cells and Totipotency Flashcards Preview

Biology-20-The Control Of Gene Expression > Stem Cells and Totipotency > Flashcards

Flashcards in Stem Cells and Totipotency Deck (20)
Loading 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