BIOLOGY OF AGING - A REVIEW

We interpreted our findings that normal human and animal cells have a finite proliferative capacity to be the expression of ageing and longe vity determination at the cell level. This finding implied the existen ce of a counting mechanism which, after a 35 year search, has now been found to he governed by diminished telomere length at each round of D NA replication. I suggest the name 'replicometer' for this mechanism b ecause replications are metered and not time, thus precluding calling this a clock or chronometer. Immortal abnormal cells, like cancer cell s, can express the reverse transcriptase 'telomerase' which maintains telomere length constant, thus providing immortality to this class of cells.