Normal Cell Growth:
Mitosis and Senescence
While scientists have known how to make cell lines since the early twentieth century, they have also discovered that most cell lines have a very limited life span.
A cell reproduces through a process called mitosis, in which it makes a copy of itself. This copy is called a "daughter cell." The video on the left shows the process of cell mitosis.
Normally, a cell can reproduce a limited number of times. After this many divisions, the daughter cells go into "senescence," which means that they can no longer divide.