In many cultures there are stories and legends that try to explain why man is mortal. In Africa, for example, legend has it that God sent a chameleon to bring immortality to mankind. But the chameleon crawled so slowly that the lizard in its mouth caught up with the death row. The seductive humanity received the message of the lizard and thus lost immortality.

Throughout the ages, philosophers have tried to answer the question, why did man die? In the fourth century BCE, the Greek philosopher Aristotle taught that the continuity of human life depends on the body's ability to balance heat and cold. He said: "Death always comes due to an insufficient amount of heat." Plato, on the other hand, taught that man has an immortal soul that continues to exist after the death of the body.

Today, although science has made huge strides, the issue in the minds of biologists about the cause of aging and death remains a mystery. London's Guardian Weeklynoted: "One of the biggest riddles facing medical science is not why people die of cardiovascular disease or cancer, but why they die even when everything is fine with them. If the cells of the body divide and continue to regenerate using this method for about 70 years, why do they suddenly, abruptly, cease to replicate themselves?"

In an attempt to understand the aging process, experts in genetics and molecular biology focused their attention on the cell. Many scientists believe that the key to a long life lies in these microscopic units. For example, there are those who predict that genetic engineering will soon allow scientists to beat cancer and heart disease. But how close is science to fulfilling humanity's dream of living forever?

Decoding the secrets of the cell

In previous generations, scientists tried to decipher the secrets of the cell, but did not have the necessary tools for this task. Only in the last century have scientists had the ability to take a closer look at a cell and study its many basic components. And what did they bring up in their wait? "The cell," says science correspondent Rick Gore, "has become a microscopic universe."

To get an idea of what about the enormous complexity of a cell, consider that each cell is made up of trillions of much smaller units called molecules. However, when the scientists examined the cell structure, they found exemplary order and evidence for the design. Philip Hennevelt, a senior lecturer in genetics and molecular biology at Stanford University, says: "The natural growth of the simplest living cell requires tens of thousands of coordinated chemical reactions." "The inherent achievements of these tiny chemical plants far exceed the capabilities of a scientist conducting laboratory experiments," he said.

Worth the challenging task of trying to prolong human life by biological means. This entails not only a deep understanding of the basic building blocks of life but also the ability to skillfully apply these building blocks! Let's take a quick look at what's going on inside a human cell to illustrate the challenge that biologists face.

Everything is written in the gardens

Each cell has a complex control center called a nucleus. The nucleus directs the cell's activities through a series of instructions encrypted in it. These instructions are stored in chromosomes.

Chromosomes are composed mainly of protein and deoxyribonucleic acid, or DNA for short.* Although scientists have known DNA since the late 1860s, it was not until 19533 that they were able to understand its molecular structure. Even then, almost another decade passed before biologists understood the "language" in which DNA molecules transmit genetic information. (See the frame on page 20.)

In the 1930s, genetics experts at the end of each chromosome discovered a short sequence of DNA that contributes to chromosome stabilization. These pieces of DNA, called telomeres and whose name is derived from the Greek words talus (tip) andmarus (part), serve a function very similar to the small dome that protects the ends of shoe laces. Without telomeres, the chromosomes would 'unravel' and break down into small parts, clinging to each other or losing their stability.

Later, the researchers noticed that telomeres are shortened in most cell types after each continuous cell division. Thus, after about 50 divisions, the telomeres decreased and turned into tiny blocks, and the cell ceased to divide and finally died. The diagnosis, that the number of cell divisions is limited and that he eventually dies, was first reported in the 1960s by Dr. Leonard Heiflick. That is why the phenomenon is now referred to by many scientists as the 'Heiflik border'.

Did Dr. Heiflik discover the cause of cell aging? Some thought so. In 1975, anatural/scientific yearbook stated that pioneers in the study of aging believed that "all living beings carry in their bodies a precise and timely mechanism for self-destruction, a kind of aging clock whose time is running out." Indeed, there were growing hopes that scientists gained a foothold in the aging process itself.

In the 1990s, scientists who studied cancer in the cells of the human body discovered another important evidence of this "cellular clock." They discovered that malignant cells had somehow learned to cancel their "cellular clock" and continued to divide endlessly. This discovery led biologists to study a very unusual enzyme, which was first discovered in the 1980s and later found in most types of cancer cells. This enzyme is called telomars. What is its function? Simply put, the telomeres can be compared to a key that refills the cell's "clock" by lengthening its telomeres.

The end of aging?

The study of telomeres quickly became one of the 'hottest' areas of molecular biology. This implies that if biologists could use telomeres to lengthen telomeres by dividing normal cells…

To read the source article click here