Judy M. Buckingham

A highly conserved repetitive DNA sequence, (TTAGGG)n, has been isolated from a human recombinant repetitive DNA library. Quantitative hybridization to chromosomes sorted by flow cytometry indicates that comparable amounts of this sequence are present on each human chromosome. Both fluorescent in situ hybridization and BAL-31 nuclease digestion experiments reveal major clusters of this sequence at the telomeres of all human chromosomes. The evolutionary conservation of this DNA sequence, its terminal chromosomal location in a variety of higher eukaryotes (regardless of chromosome number or chromosome length), and its similarity to functional telomeres isolated from lower eukaryotes suggest that this sequence is a functional human telomere.

Figure 2. Agarose gel electrophoresis of the modified vector DNA prepared with cyclic cutligation. M, DNA/ Hin dIII; lane 1, pSV-20 cut with Kpn I and Sac I; lane 2, pSV-20 prepared with cyclic cut-ligation reaction (see text for details); lane 3, the isolated 2.8-kb vector fragment; lane 4, no ligation was detected between the isolated vector fragments prepared with cyclic cut-ligation.