Do Changes in Chromosomes Cause Aging? Leonard Guarente  Cell  Volume 86, Issue 1, Pages 9-12 (July 1996) DOI: 10.1016/S0092-8674(00)80072-0

Figure 1 Structural or Functional Changes in Chromosomes That May Cause Aging (A) Telomere shortening in cultured human cells leads to cell cycle arrest (M1). If this is overridden by the action of T antigen, further shortening can lead to catastrophe (M2) due to deletion of essential genes (Greider and Harley 1996). (B) Silencing machinery that renders chromosomal domains transcriptionally inert may become inactive with age. The resulting alteration in gene expression in cells may cause a loss of cell function and aging. (C) DNA damage accumulates with age, leading to cell cycle arrest, or a defect in replication, or chromosome segregation. The identification of the WRN gene as a putative DNA helicase is superficially consistent with this view. (D) Changes in expression of rRNA occur with age due to a reduced ability to transcribe rDNA repeats or a reduction in the number of repeats due to recombination. This model arises from the link between the yeast WRN homolog and topoisomerases 2 and 3, which function in rDNA maintenance and transcription, respectively. Cell 1996 86, 9-12DOI: (10.1016/S0092-8674(00)80072-0)