telomeeri

Telomeres are repetitive nucleotide sequences found at the ends of eukaryotic chromosomes. They play a critical role in maintaining chromosomal integrity, preventing degradation, and facilitating proper cell division. Composed primarily of short, repetitive DNA sequences—typically the hexameric motif TTAGGG in humans—telomeres form protective caps that distinguish chromosome ends from DNA damage sites.

During cell division, telomeres gradually shorten due to the end-replication problem, where DNA polymerase cannot fully replicate the lagging strand at the 5' end of the chromosome. This shortening is a natural process linked to cellular aging, as critically short telomeres trigger cellular senescence or apoptosis, limiting the replicative lifespan of cells. Telomere length is influenced by genetic factors, environmental stressors, and lifestyle choices, including oxidative stress and inflammation.

Telomerase, a ribonucleoprotein enzyme, counteracts telomere shortening by adding repetitive sequences to chromosome ends. It is active in germ cells, stem cells, and some cancer cells, allowing indefinite replication. In somatic cells, telomerase activity is generally low, though it can be upregulated in response to certain stimuli or pathological conditions.

Telomere dysfunction is associated with various age-related diseases, including cardiovascular disorders, neurodegenerative conditions, and cancer. Shortened telomeres have been linked to premature aging syndromes, while dysregulated telomerase activity can contribute to tumorigenesis by evading the Hayflick limit. Research into telomere biology has implications for aging interventions, cancer therapy, and regenerative medicine, offering potential targets for extending healthy lifespan and treating degenerative diseases.