- Telomere attrition may regulate the proliferative life span of somatic cells and contribute to the genetic instability of tumour cells, and telomere maintenance is required for cell survival. The ample, but mainly correlative, evidence in support of these hypotheses is now beginning to be complemented by experimental results. There have also been unexpected findings that attest to the complexity of the biological processes and systems under study. Mammalian telomere biology has definitely entered into an exciting phase. Given the increasing pace of research on this topic, it seems most likely that a not too distant future will provide us with answers to many of the unresolved issues mentioned in this article.