Also found in: Dictionary, Thesaurus, Encyclopedia.
telomeresThe sections of DNA that forms the natural end of a CHROMOSOME. The points that resist union with fragments of other chromosomes. Telomeres consist of repeated groups of the base sequence TTAGGG, where T, A and G represent the bases thymine, adenine and guanine, respectively. Formation of telomeres involves the shaving-off of some junk DNA at the chromosome end. There is a limit to the number of times that this can occur because of the deficiency of telomerase reverse transcriptase, and this is believed to be the reason for the upper limit in the number of times cells can reproduce. Overexpression of this enzyme allows otherwise normal cells to proliferate indefinitely. Telomere length is a function of age but there is evidence that it may also be an X-linked familial trait. Telomeres and telomerase are fundamental in the biology of ageing, cancer, stem cells and the disease dyskeratosis congenita.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005