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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.

All text material ©2009 by Steven M. Carr