Listening Practice. Listen to the text and answer the questions to follow

Listen to the text and answer the questions to follow

1. How do genes affect human lifespan?

2. What is the effect of oxidation?

3. In what way does a natural substance telomerase influence the process of ageing?

4. While the scientists are still in the process of finding the secrets of longevity what can people do to improve their healthspan?

Natural selection acted to make sure that our genes were able to repair faults for only a few decades until we had passed child-bearing age. Our distant ancestors, like wild mammals today, would die from accidents, predation or infection long before they showed signs of the chronic diseases that we associate with ageing. So ageing as a means of culling the old makes little evolutionary sense.

Of course genes play a big role in determining lifespan, as the tendency for longevity to run in families shows. This is not because genes direct our death but because they control the efficiency of our cellular repair process. The most impor­tant damage may be caused by oxidation, which generates reactive "free radicals" that destroy genes and proteins.

Scientists have already discovered many specific genes that affect longevity in simple "model organisms" such as roundworms and yeast, in which the genetic link to ageing is far easier to study than in humans. Last year, US researchers identified 25 genes that influence lifespan in both worms and yeast – organisms that diverged in evolutionary terms 1.5bn years ago – and they said at least 15 of the genes had close counterparts in humans.

Knowing what many of these genes actually are, the scientists have potential targets to go after in humans and in the future they hope they could affect those targets and improve not just lifespan but healthspan.

Several genes associated with longevity have attracted particular scientific interest. The seven sirtuins are one such group of genes. They are activated by a plant chemical found in grapes, red wine and pomegranates. The research is being carried out at a US biotechnology company to develop drugs based on sirtuin. Telomerase is another natural substance that has been hailed by some as a poten­tial elixir of life. It is an enzyme whose function is to maintain the telomeres – protective DNA caps at the end of each chromosome that become slightly shorter with each cell division as we get older. Evidence is accumulating that this shortening triggers some of the negative effects of ageing at the cellular level.

Pharmaceutical researchers have been looking for drugs that could raise telomerase activity with the aim of treating age-related diseases. But it is not clear whether boosting telomerase throughout the body will reduce the general impact of ageing, and the scientists point out that turning on telomerase indiscriminately could lead to cancer, so any treatment would have to be targeted to the right cells.

There are clues that changing to a healthier lifestyle – taking more exercise, and eating more fruit and vegetables and less animal fat – increases telomerase activity in the blood. This fact has been proved by the results reported recently that telomerase levels in a group of men who made such changes increased 30 per cent.

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