telomers

Telomeres are repetitive nucleotide sequences found at the ends of eukaryotic chromosomes, serving as protective caps that prevent chromosomal degradation and fusion with neighboring chromosomes. Composed primarily of short, repetitive DNA sequences—typically TTAGGG in humans—they play a critical role in maintaining chromosomal integrity during cell division. Each time a cell divides, telomeres shorten slightly due to the end-replication problem, where DNA polymerase cannot fully replicate the lagging strand’s terminus. This gradual shortening acts as a molecular clock, limiting the number of cell divisions and contributing to cellular senescence or apoptosis.

Telomere length varies among individuals and tissues, influenced by genetic factors, aging, and environmental stressors such as oxidative damage and inflammation. Shortened telomeres are associated with accelerated aging, increased susceptibility to diseases like cancer, cardiovascular disorders, and neurodegenerative conditions. Conversely, critically short telomeres can trigger cellular senescence or apoptosis, preventing uncontrolled proliferation, which is beneficial in cancer suppression but detrimental in tissue regeneration.

Telomerase, a ribonucleoprotein enzyme, can extend telomeres by adding repetitive sequences to their ends, counteracting shortening. While telomerase is active in germ cells, stem cells, and most cancer cells to maintain proliferation, its expression in somatic cells is generally low, limiting its role in normal aging. Therapeutic strategies targeting telomerase or telomere biology are under investigation for potential applications in anti-aging research and cancer treatment, though challenges remain due to the risk of promoting tumor growth.

Maintaining telomere integrity is essential for genomic stability, and disruptions in telomere function are linked to various human diseases, emphasizing their importance in cellular biology and aging processes.