Telomeric Terminal Restriction Fragment (TRF)

Telomeres are protein-DNA structures at the ends of all eukaryotic chromosomes that are maintained by a unique ribonucleoprotein known as telomerase. This highly specialized RNA-dependent DNA polymerase provides a critical solution to the end-replication problem by adding TTAGGG repeats to 3′ ends of human chromosomes (1 –3 ). Telomere regulation is both cell cycle and developmentally-regulated, and its control is likely to be complex (4 ,5 ). There is gradual telomere shortening with age. This chromosomal pruning is presumed to be regulated by a mitotic clock, by which cell divisions are accounted (6 ,7 ). After about 100 cell divisions, a cell reaches its senescence “Hayflick” limit and cell division ceases (8 ).