All living things age, in one way or another, and despite years of research it has proved surprisingly difficult to explain why. Why, for example, do our repair mechanisms seem to become less efficient with age, so that we lose the natural resilience of youth to minor physical injury and physical stress? A hot topic in ageing research at present is the enzyme telomerase, an enzyme that maintains the protective ?seal? on the end of each chromosome. These ends are called telomeres. They prevent the chromosomes from fusing with each other to produce abnormalities, and protect the chromosome ends from being nibbled away by enzymes in the cell. Your chromosomes are precious and have to last a lifetime. They make copies of themselves at each cell division, but this also means that any damage sustained in the interim is passed on to the new cells.
Lack of telomerase results in a progressive shortening of telomeres each time cells divide, and telomere shortening has been linked to the changes seen in cultured human cells as they ?age? in their culture dishes in the laboratory. But it is not clear yet that this has anything to do with physiological ageing in humans, even though it has been shown that human body cells make very little telomerase.
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