Normal cells have a limited number of divisions, known as the Hayflick limit. This limit is primarily due to the progressive shortening of telomeres — protective caps at the ends of chromosomes. Each time a cell divides, its telomeres shorten until they reach a critical length, triggering cellular senescence or apoptosis. In cancer cells, the activation of telomerase, an enzyme that extends telomeres, allows cells to bypass this limit and continue dividing indefinitely.
