Telomeres, the ends of chromosomes, do not necessarily shorten as cells become older, as previously believed. Telomeres of cancer cells are not always uniform in length. Adjusting telomere length is therefore not a cure for cancer or aging. Instead, telomeres change size continually as cells divide.
Size is influenced by the number of proteins that attach to the telomeres.
Harrington L, et. Mammalian telomerase-associated protein. Marcand S, Gilson E, Shore D. Protein-counting mechanism for telomere length regulation in yeast.