Unit 1 KA4 Flashcards
Selective gene expression
The process by which an unspecialised cell becomes specialised.
Essential genes remain switched on, and others are switched off, so that a cell only produces proteins that are characteristic of that particular cell type.
Meristem
Regions of unspecialised plant cells that are able to divide and differentiate.
Meristems are found at the root and shoot tip (apex).
All new plant cells are produced at meristems, so growth is restricted to these areas
Division of labour
Every cell does not carry out every function.
Cells differentiate and become specialised to carry out different functions.
Stem cells
Unspecialised animal cells that can self-renew by dividing repeatedly by mitosis, and can differentiate into specialised cells when given the correct chemical signals.
Tissue (adult) stem cells
Found in tissues throughout the body.
Produce a limited range of replacement cells in the tissues where they are found, so are used for growth and repair.
Many of their genes have been switched off.
They are multipotent.
Embryonic stem cells
These are found in the blastocyst - an early embryo made of a ball of undifferentiated cells.
They are pluripotent (able to turn into all cell types), as all their genes have the potential to be switched on.
Stem cell ethics
There are ethical considerations associated with the use of stem cells, as embryos are destroyed when they are removed.
Therapeutic use of stem cells
Used to replace damaged cells/repair damaged tissues/organs.
eg. skin grafts, corneal grafts.
Potential future uses - replacement of damaged cells in Alzheimer’s or Parkinson’s disease.
Other uses of stem cells
Used for research into cell processes such as differentiation and gene regulation.
Used as model cells to study the development of diseases such as cancer.
Used for drug testing.
Mitosis
Cell division. All new body cells are produced by mitosis.
