We know that chromosomes are threadlike structures of nucleic acids and proteins, which are found in the nucleus of most living cells. They carry genetic information in the form of genes. Chromosomes are protected at their ends by a specialized structure called telomere. With each replicative cycle, the telomeres get shortened preventing uncontrolled replications. Telomeres perform several functions like protect the chromosome ends from sticking together, solve the end of replication problem, and limit the number of cell divisions. It is considered that telomeres are associated with cancer incidence and mortality. Telomere DNA has repetitive sequences (5′-TTAGGG-3′ in human), which is lengthened at the 3′ end by a special ribonucleoprotein enzyme called telomerase. Short telomeres are associated with early senescence, genomic instability, and apoptosis of cells. Short telomeres can result due to several factors including environmental factors, external factors like smoking, stress, as well as due to mutations in the components of telomere or telomerase. Short telomeres are associated with several disorders and diseases, such as dyskeratosis congenita, aplastic anemia, pulmonary fibrosis, and even cancer. Thus, it is important to understand how telomeres are associated with these diseases and what can be done to prevent such conditions.
Part of the book: Telomerase and non-Telomerase Mechanisms of Telomere Maintenance