The Teleomere problem
Each chromosome consists of a single, very
long dsDNA molecule. (Left)
Removal of lagging strand RNA primers
(in red) leaves an unpaired region at
the end of the chromosome, which if left single-stranded would be
degraded. The enzyme Telomerase adds
extra DNA onto the end of
both fragments (Centre). These Telomere sequences are stained
fluorescently in the photograph at right. Telomeric DNA may be lost
during subsequenct round of chromosome replication, without loss of
critical chromosomal DNA. Experiments
suggest that telomerase function is less efficient as cells age,
and the limited lifespan of many cell cultures, 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, Carol Greider, and John Szostak were awarded the Nobel Prize in Physiology or Medicine for 2009.
For their work on telomeres, Drs Elizabeth Blackburn, Carol Greider, and John Szostak were awarded the Nobel Prize in Physiology or Medicine for 2009.