The Cell Cycle
The cell cycle is a series of events from the time a cell forms until its cytoplasm divides. Most of the lifespan of a cell is spent in interphase and only a small fraction at the end of its lifespan is spent in the process of mitosis
The most basic function of the cell cycle is to duplicate accurately the vast amount of DNA in the chromosomes and then segregate the copies precisely into two genetically identical daughter cells. These processes define the two major phases of the cell cycle. DNA duplication occurs during S phase (S for synthesis), which requires 10–12 hours and occupies about half of the cell-cycle time in a typical mammalian cell. After S phase, chromosome segregation and cell division occur in M phase (M for mitosis), which requires much less time (less than an hour in a mammalian cell). M phase involves a series of dramatic events that begin with nuclear division, or mitosis.
This is where a normal cell spends most of its lifespan. Interphase is the interval between mitotic division when a cell grows. During this time, roughly doubles the number of its cytoplasmic components, and replicates its DNA.
G1: metabolic activities –
S: Creation of DNA
G2: creation of protein needed for cell division