テロメア | DNAセグメント、染色体保護

Telomere | DNA Segment, Chromosome Protection | Britannica Ask the Chatbot Games & Quizzes History & Society Science & Tech Biographies Animals & Nature Geography & Travel Arts & Culture ProCon Money Videos telomere Introduction References & Edit History Related Topics Videos Contents CITE verified Cite While every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions. Select Citation Style MLA APA Chicago Manual of Style Copy Citation Share Share Share to social media Facebook X URL https://www.britannica.com/science/telomere Feedback External Websites Feedback Corrections? Updates? Omissions? Let us know if you have suggestions to improve this article (requires login). Feedback Type Select a type (Required) Factual Correction Spelling/Grammar Correction Link Correction Additional Information Other Your Feedback Submit Feedback Thank you for your feedback Our editors will review what you’ve submitted and determine whether to revise the article. External Websites University of Utah - Learn.Genetics - Are Telomeres the Key to Aging and Cancer Digital Commons at Becker - Telomere biology disorders: Time for moving towards the clinic? (PDF) CellPress - Cell - Telomeres: history, health, and hallmarks of aging Nature - Scientific Reports - Telomeric DNA sequences in beetle taxa vary with species richness Healthline - Telomeres: The key to staying young and disease-free? PNAS - Biological Sciences - Telomere length is inherited with resetting of the telomere set-point American Association for the Advancement of Science - Human telomere length is chromosome end–specific and conserved across individuals Frontiers - Telomere Length as a Marker of Biological Age: State-of-the-Art, Open Issues, and Future Perspectives Biology LibreTexts - Telomere National Center For Biotechnology Information - Biochemistry, Telomere And Telomerase telomere DNA segment Ask Anything Homework Help Written and fact-checked by Britannica Editors Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree.... Britannica Editors Last updated Apr. 24, 2026 • History Britannica AI Ask Anything Table of Contents Table of Contents Ask Anything Know how telomeres protect the ends of the chromosomes and over a while, it causes cellular aging Learn how telomeres affect the aging process at the cellular level. (more) See all videos for this article telomere , segment of DNA occurring at the ends of chromosomes in eukaryotic cells (cells containing a clearly defined nucleus ). Telomeres are made up of repeated segments of DNA that consist of the sequence 5′-TTAGGG-3′ (in which T, A, and G are the bases thymine , adenine , and guanine , respectively). Some human cells contain as many as 1,500 to 2,000 repeats of this sequence at each end of each chromosome . The number of repeats determines the maximum life span of a cell: each time a cell undergoes replication, multiple TTAGGG segments are lost. Once telomeres have been reduced to a certain size, the cell reaches a crisis point and is prevented from dividing further. As a consequence, the cell dies. Thus, the processes of cell aging and cell death are regulated in part by telomeres. Telomeres are of special concern in the cellular mechanisms that underlie the development of some types of cancer . Telomeric control of cell life span appears to be inactivated by the expression of oncogenes (cancer-causing genes) or by the deactivation of tumour suppressor genes . In cells undergoing malignant transformation (progression to cancer), telomeres do shorten, but, as the crisis point nears, a formerly quiescent enzyme called telomerase becomes activated. This enzyme prevents the telomeres from shortening further and thereby prolongs the life of the cell. Most malignant tumours —including breast cancer , colorectal cancer , prostate cancer , and ovarian cancer —exhibit telomerase activity. The more advanced the cancer, the greater the frequency of detectable telomerase in independent samples. Because cell immortality contributes to the growth of many cancers, telomerase is an attractive target for the development of new anticancer drugs. Key People: Jack W. Szostak Elizabeth Blackburn Carol W. Greider (Show more) Related Topics: telomerase chromosome DNA cell death (Show more) On the Web: Digital Commons at Becker - Telomere biology disorders: Time for moving towards the clinic? (PDF) (Apr. 24, 2026) (Show more) See all related content More From Britannica cancer: Telomeres and the immortal cell Telomeres also appear to be vulnerable to genetic factors that alter an organism’s rate of aging. For example, in humans, variations in a gene known as TERC (telomerase RNA [ribonucleic acid] component), which encodes an RNA segment of the telomerase enzyme, have been associated with reduced telomere length and an increased rate of biological aging. Persons who carry these variations are suspected to be several years older biologically compared with noncarriers who are the same chronological age. TERC mutations in combination with exposure to environmental factors, such as smoking and obesity , not only quicken the pace of biological aging but also increase a carrier’s susceptibility to age-related diseases, thereby resulting in the onset of those conditions relatively early in adult life. This article was most recently revised and updated by Robert Lewis .