Gr 12-05Gr 12-06Gr

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 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 sequences are seen as fluorescently stained terminal bodies in the photograph at right. Telomeric DNA  may be lost during subsequent round of chromosome replication, without loss of critical chromosomal DNA. Experiments suggest that telomerase function is less efficient as cells age, 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, Carol Greider, and John Szostak were awarded the Nobel Prize in Physiology or Medicine for 2009.

All text material ©2014 by Steven M. Carr