:21:24
:21:48
It is thought that this limit
on somatic cell division...
:21:51
..thus limits the lifespan...
:21:54
...of higher organisms.
:21:56
Cell-lifespan is thought to be...
:21:58
...determined by "telomeres"...
:22:00
...DNA-protein complexes
at the ends of linear chromosomes...
:22:04
...that grow shorter...
:22:06
...with every cell division...
:22:09
...in the manner of coupons
being used one by one.
:22:12
But because cancer cells
can regrow their telomeres...
:22:18
...there is no limit on cell division...
:22:20
...and they will flourish forever.
:22:24
These cells came from a patient
who died of childhood cancer.
:22:28
While she is dead,
her cells live on even today.
:22:33
It's a very strange feeling.
:22:42
:22:44
:22:50
All that way to return this?
:22:53
Well, partly...