from the December 13, 2005 eNews issue
[Leia este artigo em Português]
It has been just over fifty years since the discovery of DNA - a discovery which has radically transformed modern science and changed how many look at the origin of life. The Human Genome Project has mapped our entire genetic code, which consists of a sequence of over 3 billion chemical nucleotide bases. DNA research has lead to the discovery of genetic cures for diseases. It has also resulted in faster and more accurate diagnosis of diseases, and assisted doctors in developing customized treatment plans for patients.
Although scientists have learned a great deal about the human genome, the overwhelming majority of DNA remains a complete mystery. For all the new advances made in genetics, we are constantly discovering how complex the DNA really is and how much more we have to learn. Scientists still do not know the exact number of genes, their exact locations, or their functions. Nor do they know much about gene regulation, DNA sequence regulation, chromosomal structure and organization, or non-coding DNA. The list of things we have yet to learn about DNA goes on and on. What we do know about DNA is that it is a digital, error-correcting, and self-replicating code. Within its complicated and elegant structure is held the blueprints of every living thing on the planet.
Scientists have spent years studying our genes. The human genome contains over 3 billion chemical nucleotide bases, of which the total number of genes is estimated at 30,000 to 35,000. The average gene consists of 3000 bases, but sizes vary greatly, with the largest known human gene containing 2.4 million bases. Most scientists believe the really crucial part of DNA is the genes - which codes for proteins - the so-called "building blocks of life.” A few other sections that regulate gene function are also considered useful, but the vast majority of DNA is considered simply “excess baggage.” In fact, when the Human Genome Project began some scientists only wanted to map the sections of genome that coded for protein. Mapping the rest was considered a “waste of time.” What most people don’t realize is this: not only does the function of over half our genes remain unknown, but less than 5 percent of the genome encodes for the production of proteins
So if the coding part of our DNA makes up less than 5 percent of our entire genome, what about the other 95 percent of our DNA? The other 95 percent of our DNA, which scientists have dubbed non-coding DNA, has no known function and is also referred to by scientists as “junk DNA.” Within a chromosome or a genome, the junk DNA is those portions of the DNA for which no function has been identified or intuited. In the genomes of most plants and animals, an overwhelming percentage of the DNA serves no known biological role. There are some non-coding DNA that are known to be important. These include origins of replication, which define the starting points of DNA replication and regulatory sequences, but the overwhemling majority of junk DNA remains a mystery.
One hypothesis about the junk is that these chromosomal regions are trash heaps of defunct genes, sometimes known as pseudogenes, which have been cast aside and fragmented during evolution. Some scientists believe it is the accumulated DNA of failed viruses. Yet another hypothesis is that the junk DNA provides a reservoire of sequence from which potentially advantageous new genes can emerge.
Junk DNA May Not Be Junk
However, new evidence suggests that junk DNA may not be junk after all. In recent months scientists have made several discoveries that suggest some of this previously overlooked DNA has a very specific and vital role. Scientists have found evidence to suggest that sections of non-coding DNA actually contribute to healthy limb and heart muscle development. Other sections have been found to regulate the secretion of insulin in the pancreas - a discovery which could help in developing treatments and cures for diabetes. The study of junk DNA may also help scientists understand birth defects and fight disease.
Instead of being a trash heap of failed evolutionary attempts, evidence suggests that non-coding DNA may serve a distinct and vital purpose. The patterns found in non-coding DNA are not random after all, as some scientists suspected. A study conducted last year by David Haussler of the University of California, Santa Cruz, compared the genome sequences of a man, mouse and rat. They found - to their astonishment - that several great stretches of DNA were identical across the three species. To be certain that the patterns were not simply a coincidence, they looked for sequences that were at least 200 base pairs in length. Statistically, a sequence of this length would almost never appear in all three by chance. However they did not find just one, they found 481. No less than 481 distinct sequences, each consisting of at least 200 base pairs, that were common, not only to rats, mice, and humans, but were also found in DNA samples from chickens, dogs, and fish.
Common Ancestor or Common Creator?
Most of our so-called junk DNA still remains a mystery. But whatever the function is, it is clearly of great importance. According to Professor Haussler, “the most likely scenario is that they control the activity of indispensable genes and embryo development. Nearly a quarter of the sequences overlap with genes and may help slice RNA, and the conserved elements that do not actually overlap with genes tend to cluster next to genes that play a role in embryonic development.” Researchers have begun to refer to these sequences of non-coding DNA as “conserved elements” or “ultra-conserved” DNA. They call it “ultra-conserved” because according to the evolutionary theory it has been about 400 million years since humans, rodents, chickens, and fish have shared a common ancestor, and despite 400 million years of evolution these sequences have resisted change, suggesting that any alteration of the DNA would damage the animal’s ability to survive.
Secular scientists may see these new discoveries as additional evidence that humans and animals share a common ancestor, rather than a common Creator, but we believe random chance cannot account for the complex design of DNA. It is statistically and mathematically impossible. The chances of winning the state lottery every week of your life from the age of 18 to 99 are better than the odds of a single-celled organism being formed by random chance. The probability of spontaneous generation is about the same as the probability that a tornado sweeping through a junkyard could assemble a 747 from the contents therein. It’s impossible. The evidence all points to the unavoidable conclusion that we not the product of chance or evolution, but the result of intelligent design.
Unfold the Evangel before your eyes!
Are you worn out?
Are you overwhelmed?
Are you rational?
Only rational, non-dogmatic persons can understand and accept this message. Give yourself a try. Nothing will be like before, I promise!
quarta-feira, dezembro 21, 2005