What effect do telomeres have on cell longevity?

Telomeres are repetitive DNA sequences located at the ends of chromosomes that protect them from deterioration or from fusion with neighboring chromosomes. Each time a cell divides, the DNA replication process cannot fully replicate the very end of the chromosomes, leading to a gradual shortening of the telomeres. Over time, as telomeres get shorter with each cell division, they eventually reach a critically short length, at which point the cell can no longer divide. This phenomenon is associated with cellular aging and senescence.

When telomeres become critically short, it signals the cell to enter a state of senescence, meaning the cell remains metabolically active but can no longer replicate. This is an important mechanism that helps prevent uncontrolled cellular division, which can lead to conditions such as cancer. As a result, the shortening of telomeres is considered a significant factor in determining cell longevity and lifespan, making this understanding crucial for research into aging and age-related diseases.