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How do telomeres affect cell division and aging?

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What causes our skin to wrinkle as we age? — human aging Overview of why skin ages.

Telomeres are repetitive DNA sequences located at the ends of chromosomes that function as protective caps. Their primary role in cell division and aging is to regulate the number of times a cell can replicate.12

During each round of cell division, the replication process fails to copy the very end of the chromosome, causing a portion of the telomere to be lost. As these sequences shorten with successive divisions, the cell eventually reaches a "crisis point" where it can no longer divide, leading to senescence or cell death. This mechanism serves as a biological clock that limits the life span of a cell.12

While most somatic cells experience this progressive shortening, some cells—such as germ cells and certain cancer cells—activate the enzyme telomerase. Telomerase adds nucleotides to telomeres, preventing their erosion and allowing these cells to escape senescence and continue dividing indefinitely. Conversely, genetic mutations or environmental factors that accelerate telomere shortening are linked to premature biological aging and an increased risk of age-related diseases.12