According to the cellular clock theory, after about 70 or 80 replications, the cell can no longer reproduce and the are dramatically reduced.

According to the cellular clock theory, after about 70 or 80 replications, the cell can no longer reproduce and the telomeres are dramatically reduced.  

Cellular clock theory is one of the biological theories of ageing. Leonard Hayflick first suggested this theory and he found that cells can divide maximum 100 times during the life. He showed that cells isolated from individuals between 50 and 70 years old had divided fewer than 100 times and that the total number of cell divisions was roughly related to the age of the individual.

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