The consequences when these ends or 'telomeres' get too short can be drastic. Pieces of chromosomes may break off and be destroyed, or become attached to other chromosomes. The damage gets worse as the cells replicate further. This plays havoc with the functions of the genes encoded by the DNA, giving rise to cells that grow and spread uncontrollably. Mice and humans suffer from different types of cancer.
Mice have long telomeres that are resilient to cell division, unlike human telomeres.
So it was thought that mice mainly suffer from cancers that are not related to telomere damage. DePinho's team worked with mutant mice lacking the telomerase gene. They shortened the animals' telomeres by inter-breeding them for several generations. Mice lacking both p53 and telomerase suffered mainly from malignancies of body linings, or 'epithelia', such as the gut wall. Mice lacking only p53 developed different cancers, the researchers report.