Finding
Treasure in Trash
from the December
13, 2005 eNews by Chuck Missler
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.
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