Telomeres and Aging: Is there a connection?. Group activity. Using texts in the back, construct a drawing of a typical chromosome. Also, include a drawing of a double chromosome on the same page. Label all parts. What are telomeres?. Telomeres are…
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It has been proposed that telomere shortening may be a molecular clock mechanism that counts the number of times a cell has divided and when telomeres are short, cellular senescence (growth arrest) occurs.
Geron Corporation likens the telomere and aging condition to this:
For the cell, having a long telomere can be compared to having a full tank of gas in your automobile; having a short telomere is like running on empty. Each time a cell divides, its telomeres become a little shorter until the cells simply can no longer divide (e.g., it runs out of fuel).
“After a certain number of cell divisions, the telomeres would be so short as to somehow prevent the cell from further proliferation--putting it in a state called senescence. In other words, he proposed that telomere length offered a clock for telling a cell's longevity.” - Scientific American
Dr. Jerry Shay and his colleagues (The University of Texas Southwestern Medical Center at Dallas ) found that cellular aging can be bypassed or put on hold by the introduction of the catalytic component of telomerase (i.e., the fuel added to the gas tank to keep the car running)!
In the laboratory, cells in tissue culture with introduced telomerase have extended the length of their telomeres. They have already divided for 250 generations past the time they normally would stop dividing, and are continuing to divide normally, giving rise to normal cells with the normal number of chromosomes.
Research also shows that the counter that controls the wasting away of the telomere can be "turned on" and "turned off". The control button appears to be an enzyme called telomerase which can rejuvenate the telomere and allow the cell to divide endlessly. Most cells of the body contain telomerase but it is in the "off" position so that the cell is mortal and eventually dies.
The telomerase control gene has been mapped to 3p21 (chromosome 3, the p (short) arm, locus 21)
Although the gene for telomerase is present in all cells, hTRT is present only in immortal cells, where it serves to fuse the repeating sequences of DNA to the chromosomes, thereby lengthening the telomeres.