Telomerase adds telomeric sequences to the ends of each chromosome. The human genes encoding the telomerase and telomerase associated RNA are active in germ and stem cells but are turned off in most adult cells.
- The telomere is a DNA sequence at the end of each chromosome that becomes progressively shorter with each division the cell undergoes.
- When it is reduced to a critical length the cell is not capable of dividing, the enzyme telomerase is able to lengthen the telomere thus preventing this from occurring.
- Telomeres are repeating hexameric sequences of TTAGGG found at the end of chromosomes
- They shorten with age and cell replication
- The presence of telomerase as is seen in germ cells maintains the telomeres
- The loss of telomerase activity in somatic cells leads to telomeres shortening
- The reactivation of telomerase in some cancer cells improves their survival and may give them "immortality"
- Those with the premature ageing condition (Progeria) have short telomeres