BIOLOGY

The question of immortality

Telomers: Repeating DNA sequences that protect the ends of chromosomes and shorten with each round of DNA replication. Each cell comes with built-in limit on the number of divisions it can undergo. As we age, our cellular death clock is ticking along and the telomeres at the ends of our chromosomes fray with each cell division. When the telomeres reach the critical length, the cell will stop dividing and die.

Turritopsis dohrnii: (The immortal jellyfish): a species of small jellyfish that exhibits an exceptional and unique ability to avoid death. Under certain circumstances, its medusa form shrinks and undergoes a retrograde transformation to a juvenile morph - the polyp. Theoretically, this process of metamorphosis in a direction opposite to the typical ontogenetic path (transdifferentiation) can go on indefinitely, effectively rendering the jellyfish biologically immortal.