Specialisation
Specialisation of cells leads to the formation of a variety of cells, tissues and organs.
Groups of organs which work together form systems.
A hierarchy exists:
- cells –> tissues –> organs –> systems
Mitosis
Sequence of events of mitosis:
- chromosomes shorten and thicken
- chromosomes move to the equator of the cell
- pairs of chromatids are pulled apart by spindle fibres
- nuclear membranes form
- cytoplasm divides
Mitosis provides new cells for growth and repair of damaged cells and maintains the diploid chromosome complement.
Diploid cells have two matching sets of chromosomes, which are replicated during mitosis.
Haploid cells have one set of chromosomes, such as the gametes (egg and sperm).
Stem cells
Stem cells in animals are unspecialised cells which can divide in order to self-renew.
They have the potential to become different types of cell.
Stem cells are involved in growth and repair.
Stem cells can be obtained from the embryo at a very early stage.
In addition, tissue stem cells can be found in the body throughout life.