First 288 words of the document:
3.5.7 Gene expression is controlled by a number of features
TOTIPOTENCY AND CELL SPECIALISATION
What are totipotent cells?
Totipotent cells are cells which can mature into any body cell.
Specialisation: The process of a totipotent cell becoming specialised to
express one gene.
Specialised: The cell has a specific function e.g. alpha and beta cells in
the islets of Langerhans.
Stem cells: Undifferentiated dividing cells that occur in adult animal
Where are totipotent cells?
Embryos embryonic stem cells are found when the egg is fertilised,
none of the cells are specialised. They have to differentiate into their
Stem cells found in the small intestine, bone marrow and skin of
Plants in plants, many of the cells remain unspecialised. They can
develop in vitro or into organs that the plant needs. (Taking a root cell
from a plant and placing it in the right conditions can create an identical
clone of the plant it was take from.)
How does a cell become specialised?
A cell becomes specialised by only expressing
certain genes. If it expressed all the genes in
the DNA then it would be a waste of time and
energy. All cells express certain genes e.g.
chemicals for respiration. This specialisation
can change the appearance of a cell due to
the protein genes that are being expressed.
How are genes prevented from being expressed?
Regulating transcription so there's no mRNA to be translated
Regulating translation so the genetic code is not revealed
Ethics Surrounding Embryonic Stem Cells
Other pages in this set
Here's a taster:
Gene expression is controlled by a number of features
Embryo at this stage has no Undermines respect for human
resemblance to a human being life. Playing `god'.
and is just cells. Lead to older foetuses/babies
Wrong to allow human being used.
suffering which can be Lead to human cloning,
prevented. research could be used in other
Why destroy embryos after countries.
IVF? Wrong to use as a means to an