The Teleomere problem
chromosome consists of a single, very
long dsDNA molecule.
Removal of lagging strand RNA primers
(in red) leaves an unpaired region at
the very end of the molecule, which if left
single-stranded would be
degraded, also exposing the paired ssDNA region..
The enzyme Telomerase adds
extra DNA onto
the end of
both fragments, based on an RNA template (centre). These Telomere
seen as fluorescently stained terminal bodies in the
photograph at right. Telomeric
DNA may be lost
during subsequent round of chromosome replication, without
critical chromosomal DNA.
suggest that telomerase function is less efficient as
and that the limited lifespan of cells in culture, and
perhaps aging of in
vivo cells as well, is a
function of the loss of critical DNA.
For their work on telomeres, Drs Elizabeth Blackburn,
and John Szostak
were awarded the Nobel Prize in Physiology
or Medicine for