2.2 Growth and Differentiation
The cells of a multicellular organism are not all the same. This is because as they grow, they begin to differentiate. This is when cells become specialised to carry out a certain function, as some of their genes have been switched on and others have been switched off so they have certain sub-cellular structures specific to their function.
This is important so that if certain cells are dead or damaged, they can be replaced.
Stem cells: unspecialised cells that can differentiate into other types of specialised cells.
Most specialised cells can only form the same type of cell. Some differentiated cells (ie: red blood cells, skin cells) cannot divide so adult stem cells replace them.
Nerve cells don’t divide once they have differentiated and aren’t replaced by stem cells, so when they are damaged/die, they aren’t replaced.
Most plant cells are able to differentiate throughout their lives. Undifferentiated stem cells (meristem) are found in the stems and roots.
Even if a plant cell has differentiated, it is able to redifferentiate into another specialised cell.
Cloning: producing identical offspring.
Huge numbers of plant clones can be produced from a tiny leaf tissue, all identical to the original parent. It is difficult to clone animals, as most animal cells differentiate permanently in early embryo development.
The cells of a multicellular organism are not all the same. This is because as they grow, they begin to differentiate. This is when cells become specialised to carry out a certain function, as some of their genes have been switched on and others have been switched off so they have certain sub-cellular structures specific to their function.
This is important so that if certain cells are dead or damaged, they can be replaced.
Stem cells: unspecialised cells that can differentiate into other types of specialised cells.
Most specialised cells can only form the same type of cell. Some differentiated cells (ie: red blood cells, skin cells) cannot divide so adult stem cells replace them.
Nerve cells don’t divide once they have differentiated and aren’t replaced by stem cells, so when they are damaged/die, they aren’t replaced.
Most plant cells are able to differentiate throughout their lives. Undifferentiated stem cells (meristem) are found in the stems and roots.
Even if a plant cell has differentiated, it is able to redifferentiate into another specialised cell.
Cloning: producing identical offspring.
Huge numbers of plant clones can be produced from a tiny leaf tissue, all identical to the original parent. It is difficult to clone animals, as most animal cells differentiate permanently in early embryo development.
