The regular and repeated sequence of cell growth and division is known as the cell cycle. The cell cycle consists of mitosis and cytokinesis and takes place after the completion of the three preparatory phases (G1, S, and G2) that constitute interphase.
Interphase - Three preparatory phases
• G1 - a period of intense biochemical activity. The cell doubles in size. Cytoplasmic structures such as ribosomes, mitochondria and enzymes increase in number. Membranous structures such as the endoplasmic reticulum, golgi complex, vacuoles, vesicles and lysosomes are renewed and increase.
- Mitochondria and chloroplast replicate.
• S - The process of DNA replication occurs at this stage.
• G2 - Chromosomes slowly begin to coil and condense. Cell structures required for mitosis begin to assemble.
Mitosis - Nuclear division characterized by chromosome replication and allocation to two separate daughter nuclei.
Cytokinesis - process that follows mitosis that divides the cell into two new daughter cells.
2 x 1012 cell divisions/24 hours
25 million cell divisions per second