A telomere is a region of repetitive DNA at the end of a chromosome, which protects the end of the chromosome from deterioration. Its name is derived from the Greek nouns telos (τἐλος) "end" and merοs (μέρος, root: μερ-) "part".
Russian theorist Alexei Olovnikov was the first to recognize (1971) the problem of how chromosomes could replicate right to the tip, as such was impossible with replication in a 5' to 3' direction. To solve this and to accommodate Leonard Hayflick's idea of limited somatic cell division, Olovnikov suggested that DNA sequences would be lost in every replicative phase until they reached a critical level, at which point cell division would stop.
During cell division, the enzymes that duplicate the chromosome and its DNA cannot continue their duplication all the way to the end of the chromosome. If cells divided without telomeres, they would lose the ends of their chromosomes, and the necessary information they contain. (In 1972, James Watson named this phenomenon the "end replication problem".) The telomeres are disposable buffers blocking the ends of the chromosomes and are consumed during cell division and replenished by an enzyme, the telomerase reverse transcriptase.
Elizabeth Blackburn compared telomeres to the aglets (tips) on the ends of shoelaces that keep them from fraying.
In 1975–1977, Blackburn, working as a postdoctoral fellow at Yale University with Joseph Gall, discovered the unusual nature of telomeres, with their simple repeated DNA sequences composing chromosome ends. Their work was published in 1978. The telomere shortening mechanism normally limits cells to a fixed number of divisions, and animal studies suggest that this is responsible for aging on the cellular level and sets a limit on lifespans. Telomeres protect a cell's chromosomes from fusing with each other or rearranging—abnormalities which can lead to cancer—and so cells are normally destroyed when their telomeres are consumed. Most cancers are the result of "immortal" cells which have ways of evading this programmed destruction.
Elizabeth Blackburn, Carol Greider, and Jack Szostak were awarded the 2009 Nobel Prize in Physiology or Medicine for the discovery of how chromosomes are protected by telomeres and the enzyme telomerase.
Telomeres and telomerase: biological and clinical importance ...
(15) developed an assay for testing telomerase activity in cell extracts. Based on identification of telomerase mechanisms and properties, the telomere ...
www.clinchem.org/cgi/content/full/43/5/708
Telomere Length Analysis and In Vitro Telomerase Assay.
1 Introduction; 2 Materials and Methods; 2.1 Telomere Measurement; 2.2 Telomere Cloning; 2.3 TRAP Telomerase Assay; 3 Notes; References. Browse by Subject ...
www.springerprotocols.com/Abstract/doi/10.../1-59259-434-4:123
Facts about Telomeres and Telomerase
The following section will teach you the basics of telomeres and telomerase. It will also introduce you to the potential applications of current telomerase ...
www4.utsouthwestern.edu/cellbio/shay.../sw_facts.html
TRAP–LIG, a modified telomere repeat amplification protocol assay to quantitate telomerase inhibition by small molecules.
Its major function is to maintain the length of telomeric DNA by synthesizing telomeric DNA repeats, and its enzymatic activity is assayed by means of the ...
linkinghub.elsevier.com/retrieve/pii/S0003269708002960
Telomeres and Telomerase: The Cellular Timekeepers
The telomeres appear to be the cellular timekeepers, but are they related to human aging?
www.senescence.info/telomeres.html
Effect of Telomere and Telomerase Interactive Agents on Human Tumor and Normal Cell Lines.
The cytotoxic effect of telomere and telomerase interactive agents against normal human marrow cells in the colony-forming assay showed the same range of ...
clincancerres.aacrjournals.org/content/
Cell Research - Telomere and telomerase in oncology
Shortening of the telomeric DNA at the chromosome ends is presumed to limit the lifespan of... Telomere, telomerase, cancer, telomerase assay, inhibitor ...
www.nature.com
Telomeres and telomerase — Genes & Development
Cdc13p (gray) and Est1 (purple) may recruit telomerase to the telomeric 3′ end in ..... (1995) An in vitro assay for Saccharomyces telomerase requires EST1. ...
genesdev.cshlp.org/content/13/18/2353.full
Telomerase Assay in Renal Cancer
Bacchetti, S. and Counter, C. M. (1995) Telomeres and telomerase in human cancer. ...quantitative nonisotopic assay for telomerase activity in humantumors. ...
www.springerprotocols.com/Abstract/doi/10.1385/1-59259-144-2:05
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