The Search for the “Immortality” Gene
MANY civilizations have stories and fables that attempt to explain mankind’s mortality. In Africa, for example, one legend has it that a chameleon was sent by God to bring immortality to mankind, but it traveled so slowly that another lizard, carrying the message of death, arrived first. Gullible mankind accepted that lizard’s message and thus lost out on immortality.
Over the centuries philosophers have likewise attempted to answer the question, Why does man die? In the fourth century B.C.E., the Greek philosopher Aristotle taught that the continuation of a person’s life hinged on the body’s ability to balance heat and cold. He said: “It is always to some lack of heat that death is due.” Plato, on the other hand, taught that man has an immortal soul that survives the death of the body.
Today, despite the amazing advances of modern science, biologists’ questions about why we grow old and die remain largely unanswered. Said The Guardian Weekly of London: “One of the great mysteries of medical science has been not why people die of cardiovascular disease or cancer: it was why they die even when there is nothing wrong at all. If human cells divide, and go on renewing themselves by division for 70 years or so, why should they suddenly stop replicating all at once?”
In their quest to understand the aging process, geneticists and molecular biologists have turned their attention to the cell. Many scientists feel that within these microscopic units, the key to longer life can be found. Some, for instance, predict that genetic engineering will soon allow scientists to conquer cancer and heart disease. But how close is science to fulfilling mankind’s dream of living forever?
Unlocking Secrets of the Cell
Previous generations of scientists attempted to unlock secrets of the cell, but they lacked the necessary tools to do so. It has only been within the last century that scientists have had the ability to peer inside a cell and observe many of its basic components. What have they found? “The cell,” says science writer Rick Gore, “has turned out to be a microuniverse.”
To get some idea of the enormous complexity of a cell, consider that each one is made up of trillions of much smaller units called molecules. Yet, when scientists observe the structure of a cell, they find tremendous order and evidence of design. Philip Hanawalt, assistant professor of genetics and molecular biology at Stanford University, says: “The normal growth of even the simplest living cell requires that tens of thousands of chemical reactions occur in coordinated fashion.” He also states: “The programmed accomplishments of these tiny chemical factories go far beyond the capabilities of the scientist in his laboratory.”
Imagine, then, the daunting task of trying to extend the human life span through biological means. It would require not only a deep understanding of the basic building blocks of life but also the ability to manipulate those building blocks! Let us take a brief look inside a human cell to illustrate the challenge facing biologists.
It’s All in the Genes
Within each cell is a complex control center called a nucleus. The nucleus directs the cell’s activities by following a set of coded instructions. These instructions are stored in the chromosomes.
Our chromosomes consist primarily of protein and deoxyribonucleic acid, or DNA for short. * Although scientists have known about DNA since the late 1860’s, it was not until 1953 that its molecular structure was finally understood. Even then, it took nearly a decade more before biologists began to understand the “language” DNA molecules use to carry genetic information.—See the box, page 22.
In the 1930’s, geneticists found that at the tip of each chromosome is a short sequence of DNA that helps to stabilize the chromosome. Named telomeres, from the Greek teʹlos (end) and meʹros (part), these snippets of DNA act much like the protective end cap on a shoelace. Without telomeres, our chromosomes would tend to unravel and break into short segments, stick to one another, or otherwise become unstable.
Researchers later observed, however, that in most types of cells, the telomeres became shorter after each successive division. Thus, after 50 or so divisions, the cell’s telomeres were whittled down to tiny nubs, and the cell stopped dividing and eventually died. The observation that cells appear to be limited to a finite number of divisions before they die was first reported in the 1960’s by Dr. Leonard Hayflick. Hence, the phenomenon is now referred to by many scientists as the Hayflick limit.
Did Dr. Hayflick discover the key to cellular aging? Some thought so. In 1975 the Nature/Science Annual said that the avant-garde in the field of aging believed that “all living creatures carry around within themselves a precisely timed self-destruct mechanism, a clock of aging that ticks away vitality.” Indeed, hope began to grow that scientists were finally beginning to zero in on the aging process itself.
In the 1990’s, researchers studying human cancer cells discovered another important clue regarding this “cellular clock.” They found that malignant cells somehow learned how to override their “cellular clock” and divide indefinitely. This discovery led biologists back to a most unusual enzyme, first discovered in the 1980’s and later found to be present in most types of cancer cells. That enzyme is called telomerase. What does it do? Simply put, telomerase can be likened to a key that resets a cell’s “clock” by lengthening its telomeres.
End to Aging?
Telomerase research soon became one of the hottest fields in molecular biology. The implication was that if biologists could use telomerase to offset the shortening of telomeres when normal cells divide, perhaps aging could be halted or at least substantially delayed. Interestingly, Geron Corporation News reports that researchers experimenting with telomerase in the laboratory have already demonstrated that normal human cells can be altered to have “an infinite replicative capacity.”
In spite of such progress, there is little reason to expect that in the near future, biologists will appreciably extend our life span with telomerase. Why not? One reason is that aging involves much more than deteriorating telomeres. Consider, for instance, the comments of Dr. Michael Fossel, author of the book Reversing Human Aging: “If we conquer aging as we know it today, we will still age in some new, less familiar way. If we extend our telomeres indefinitely, we may not acquire the diseases we now associate with old age, but we will still eventually wear out and die.”
Indeed, there are likely a number of biological factors that contribute to the aging process. But the answers at present remain locked up beyond the reach of scientists. Leonard Guarente of the Massachusetts Institute of Technology says: “Right now aging is still very much a black box.”—Scientific American, Fall 1999.
While biologists and geneticists continue to probe the cell to understand why mankind grows old and dies, God’s Word reveals the real reason. It simply states: “Through one man sin entered into the world and death through sin, and thus death spread to all men because they had all sinned.” (Romans 5:12) Yes, human death results from a condition that science will never be able to cure—inherited sin.—1 Corinthians 15:22.
On the other hand, our Creator promises to undo the effects of inherited sin by means of Christ’s ransom sacrifice. (Romans 6:23) We can be certain that our Creator knows how to reverse aging and death, for Psalm 139:16 says: “Your eyes saw even the embryo of me, and in your book all its parts were down in writing.” To be sure, Jehovah God originated the genetic code and put it down in writing, as it were. Thus, in his due time, he will see to it that our genes permit everlasting life for those who are obedient to his requirements.—Psalm 37:29; Revelation 21:3, 4.
^ par. 12 For a detailed description of DNA, see Awake!, September 8, 1999, pages 5-10.
[Box on page 22]
THE “LANGUAGE” OF DNA
The basic units, or “letters,” of the DNA language are chemical components called bases. There are four types of bases: thymine, adenine, guanine, and cytosine, usually abbreviated T, A, G, and C. “Think of those four bases as letters in a four-letter alphabet,” says National Geographic magazine. “Just as we arrange the letters of our alphabet into meaningful words, the A’s, T’s, G’s, and C’s that make up our genes are arranged into three-letter ‘words’ comprehensible to the machinery of the cell.” In turn, genetic “words” form “sentences” that tell the cell how to manufacture a particular protein. The order in which the DNA letters are strung together determines whether the protein will function as an enzyme that helps you to digest your supper, an antibody that wards off an infection, or any of the thousands of proteins that are found within your body. Little wonder that the book The Cell refers to DNA as “the basic blueprint of life.”
[Picture on page 21]
The tips on chromosomes (shown here glowing) allow cells to keep dividing
Courtesy of Geron Corporation