Telomeres are essential structures found at the ends of eukaryotic chromosomes, composed of non-coding DNA that consists of repeating sequences. Unlike prokaryotic chromosomes, eukaryotic chromosomes rely on telomeres to protect their genetic information during cell division. Each time a cell undergoes DNA replication, telomeres shorten, which has been associated with the aging process. This gradual shortening serves as a biological clock, signaling normal cells to cease division when telomeres become critically short, ultimately leading to cell death.
In a typical eukaryotic chromosome, the coding DNA is located in the internal regions, while telomeres are positioned at the tips. As cells replicate, the chromosomes progressively shorten, indicating that longer telomeres are characteristic of younger cells, whereas shorter telomeres are indicative of older cells. This relationship between telomere length and cellular age highlights the role of telomeres in the aging process.
Interestingly, some cells express an enzyme known as telomerase, which can counteract telomere shortening. Telomerase catalyzes the addition of DNA sequences to the telomeres, effectively maintaining their length. This enzyme is predominantly found in germ cells, which are precursors to gametes, and in many cancer cells. The presence of telomerase allows these cells to bypass the normal signals that would halt cell division due to telomere shortening, enabling continuous proliferation. Understanding the dynamics of telomeres and telomerase is crucial for insights into aging and cancer biology.