Telomeres are Located at the Ends of Linear Chromosomes and are Composed of Hundreds to Thousands of TTAGGG Repeats Coated by Specialized Proteins Collectively Termed Shelterin. As the cell divides, telomeres shorten due to DNA polymerase’s inability to fully replicate the telomeres. If the cell expresses telomerase (right side of the Figure), telomere lengths are maintained, preserving cellular proliferative capacity. If telomerase is absent or impaired (left side of the Figure), telomeres progressively shorten, eventually reaching critical length, inducing cell senescence, apoptosis, and chromosomal instability. These processes may be clinically translated into disease.