テロメア

Telomere Scan to visit Skip to main content ​Telomere updated: May 6, 2026 Definition A telomere is a region of repetitive DNA sequences at the end of a chromosome. Telomeres protect the ends of chromosomes from becoming frayed or tangled. Each time a cell divides, the telomeres become slightly shorter. Eventually, they become so short that the cell can no longer divide successfully, and the cell dies. Narration Telomere. A chromosome is essentially a long, long piece of DNA that has really wrapped up and compacted on itself until it looks like the structure you probably picture when I say chromosome. The problem is that the long piece of DNA has two ends, and they're just hanging out there loose. A lot of things could go wrong if those ends aren't protected. They could get cut off, or they could join onto other loose DNA ends, which would be a problem for the cell. Telomeres are how cells protect chromosome ends. The telomere itself is a long stretch of a specific short DNA sequence repeated over and over hundreds of times. At the very end of the telomere is a sort of knot not called the "T-loop," which keeps the chromosome ends from all sticking together. Every time a cell divides, some of those telomere repeats get cut off. So in certain cell types that divide a lot, an enzyme called "telomerase" adds those repeats back so the telomere doesn't get too short. Lisa H. Chadwick, Ph.D. Deputy Director Division of Genome Sciences Search Back to Glossary Related Centromere Chromatid Chromosome Deoxyribonucleic Acid (DNA)