The division of animal cells, or mitosis, involves division of the nucleus and cytokinesis, or division of the cytoplasm. Identical copies of all 23 chromosomes are present in both the original and two daughter cells that result.
Cellular mitosis in animals follows several steps: interphase, prophase, metaphase, anaphase, telophase and cytokinesis.
- Interphase - the cell prepares for division during this "resting" cycle; during this period DNA may begin to replicate but chromosomes are not visible
- Prophase - chromatin begins to condense into chromosomes; centrioles form and move to opposite ends of the cell; the nuclear membrane dissolves and the mitotic spindle begins to form
- Metaphase - spindle fibers begin to align the chromosomes towards the center or equator of the cell, pairing them to ensure the equal division of chromosomes in subsequent phases
- Anaphase - the spindles begin to shorten which pulls the paired sets of chromosomes apart, ensuring that each daughter cell gets an identical set
- Telophase - chromosomes decondense and become less visible; new membranes begin to form over the nuclei of the daughter cells
- Cytokinesis - cell cleavage occurs, first appearing as a shallow groove in the cell which causes the formation of a fibrous ring of actin, which is a protein. In effect, this ring closes, pinching off the two daughter cells