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Mortality and immortality at the cellular level. A review
1University of California, San Francisco, The Sea Ranch 95497, USA. hayflick.leonard@gene.com
Biochemistry. Biokhimiia
|February 19, 1998
Summary
Normal cells have a limited number of replications due to telomere shortening, a process proposed to be a
Area of Science:
- Cellular biology
- Gerontology
- Molecular biology
Background:
- Historically, normal cells were believed to have unlimited replication capacity.
- This view shifted in the 1960s with the discovery of finite cellular replicative capacity.
- Aging was not initially linked to intracellular events.
Purpose of the Study:
- To investigate the mechanism behind the finite replicative capacity of normal cells.
- To identify the cell division counting mechanism.
- To understand the relationship between telomere length and cellular lifespan.
Main Methods:
- Review of historical cell culture research.
- Analysis of telomere shortening in normal cells during DNA replication.
- Comparison of telomere maintenance in normal versus immortal cells.
Main Results:
- Normal cells exhibit telomere shortening with each DNA replication cycle.
- Immortal cells maintain telomere length using the enzyme telomerase.
- Telomere shortening acts as a replicometer, counting DNA replications, not time.
Conclusions:
- Telomere shortening and finite cell lifespan likely determine longevity, not aging.
- The hundreds of biological changes preceding replicative senescence are age-related changes.
- The proposed term 'replicometer' accurately describes the telomere shortening mechanism.