Final answer:
Telomeres are made up of repetitive, noncoding DNA sequences that protect chromosomes from degradation, and the enzyme telomerase, containing a protein and RNA component, adds these sequences to maintain telomere length. Telomerase activity varies, being higher in stem and cancer cells, which promote longevity and proliferation, respectively.
Step-by-step explanation:
Telomeres are the protective caps at the ends of linear chromosomes, consisting of noncoding, repetitive DNA sequences. In humans, the telomere sequence is TTAGGG, which is repeated between 100 to 1000 times, depending on the cell type. These sequences safeguard the genetic data by preventing the loss of coding sequences during cell division. Telomerase plays a critical role in lengthening telomeres by adding these sequences to chromosome ends. It is made up of a protein component with reverse transcriptase activity, known as Telomerase Reverse Transcriptase (TERT), and an RNA component that serves as a template for adding DNA nucleotides.
Telomerase binds to telomeres during the S phase of the cell cycle to maintain telomere length, especially in rapidly dividing cells like stem cells and cancer cells. In most somatic cells, notably adult cells, telomerase activity is low or absent, leading to gradual telomere shortening and eventual cell aging or senescence. However, in stem cells and cancer cells, telomerase activity is typically higher, promoting cell longevity and, in the case of cancer, unchecked cell proliferation. Understanding the regulation of telomerase activity is thus crucial in fields such as aging research and cancer therapy.