What are telomeres and what do they do?
Telomeres are repeated DNA sequences that protect the ends of chromosomes from being treated like a broken piece of DNA needing repair. Without telomeres, the ends of the chromosomes would be “repaired”, leading to chromosome fusion and massive genomic instability. Telomeres are also thought to be the “clock” that regulates how many times an individual cell can divide. Telomeric sequences shorten each time the DNA replicates. When at least some of the telomeres reach a critically short length, the cell stops dividing (is senescent) which may cause or contribute to some age-related diseases. In cancer, a special cellular reverse transcriptase, telomerase, is reactivated and maintains the length of telomeres, allowing tumor cells to continue to proliferate. Telomeres do not contain genes but are repetitive DNA elements that are expendable and thus their loss may not appear to affect cellular function until they reach a very short length.
