telomeere

Telomeres are specialized structures found at the ends of eukaryotic chromosomes. They consist of repetitive DNA sequences, typically TTAGGG in humans, and are capped with proteins that protect the ends of chromosomes from degradation and fusion. Telomeres play a crucial role in maintaining genomic stability and are essential for cell division. As cells divide, telomeres shorten due to the end replication problem, a phenomenon where the lagging strand of DNA cannot be fully replicated. This shortening can lead to cellular senescence or apoptosis, limiting the lifespan of cells. Telomerase, a ribonucleoprotein enzyme, can counteract this process by adding nucleotides to the ends of telomeres, thereby extending their length. Telomerase activity is generally high in stem cells and cancer cells, which allows them to divide indefinitely. In contrast, most somatic cells have low telomerase activity and are subject to the Hayflick limit, a finite number of divisions before they can no longer divide. Telomeres also play a role in DNA damage response and are involved in the regulation of gene expression. The study of telomeres has significant implications for aging, cancer, and genetic disorders.