arby focuses on the alluded "cosmic serpent" and the origin of life. He was looking for the relation between this "cosmic serpent" and DNA. He thus finds that the DNA representation is in all points similar to what the serpent symbolizes.
Stretching the DNA contained in the nucleus of a human cell, we obtain a two-metre-long thread with a diameter of just a few atoms. This thread is one billion times longer than its own width. Keeping the proportions, it is as if our little finger stretched from Paris to Los Angeles.
A DNA thread is much smaller than visible light perceived by humans. Even going beyond the limits of the naked eye with the most powerful optic microscopes, it is impossible to perceive it: DNA is approximately one hundred and twenty times thinner than the smallest wavelength of visible light.
The nucleus of a cell measures approximately as much as the two-millionth part of a pin head. DNA, two metres long, is compacted inside this minute volume wrapping itself ad infinitum, thus combining extreme length with infinitesimal smallness.
An average human being is formed by nearly one hundred billion cells.
This means there are two hundred billion kilometres of DNA in a human body - equivalent to seventy round trips from the Sun to Saturn. You could travel your whole life in a Boeing 747 at full speed and you would not even reach one hundredth part of this distance. Your personal DNA is capable of coiling round the Earth five million times.
All the cells in the world - human, animal, vegetal or bacterial - contain DNA. On the other hand, they are all full of salty water, a content of mineral salts that resembles the one of primitive oceans: we weep and transpire what is essentially sea water. So DNA is bathed in water, and this plays a crucial role in establishing its shape and, therefore, its function. In fact, the aquatic medium confers DNA its intertwined ladder shape, because the four DNA bases (Adenine, Guanine, Cytosine and Thymine) are insoluble in water and turn towards the molecule interior to form, by joining in couples, the steps of the ladder; they then wrap around themselves to avoid any contact with the wet environment that surrounds them.
So the DNA molecule is a long chain formed by two intertwined ribbons bound together by four bases. These bases can only join forming specific couples - A with T, G with C. This implies that one of the two ribbons is a duplicate of the other one and that the genetic message is double: it contains a main text on one of the ribbons which is read in a precise direction by reading enzymes, and a complementary reserve text which is not read because it is inverted.
The second ribbon plays two essential roles. It allows repairing enzymes to rebuild the main text in case it has been damaged, and, above all, it supplies the mechanism for the reproduction of genetic messages. In fact, it is enough to open the double helix like a zipper to obtain two separate and complementary ribbons which can then be immediately rebuilt into double ribbons by duplication enzymes. These enzymes can only couple an A with a T, and so on, since any other base coupling is impossible. This process allows the reconstitution of two twin double helixes, identical to the original at all levels.
Without this duplication mechanism, a cell could never divide and life would not exist.
DNA is the information molecule of life and its essence consists in being, at the same time, simple and double.
DNA and its duplication mechanisms are the same for all living beings.
From one species to the other the only change is in the order of letters. This constancy goes back to the very origins of life on Earth. According to biologist Robert Pollack: "The surface of the planet has changed many times, but DNA and its duplication cellular machinery have remained constant. Schrödinger has said that DNA was an non periodic crystal, but this minimizes its stability: no stone, no mountain, no ocean, nor even the sky over our heads has remained so stable and constant over such a period of time. There is nothing inanimate, whatever its complexity, which has lasted without changes even for a fraction of the time that DNA and its duplication machinery have coexisted."
At the beginning of its existence, about four thousand five hundred million years ago, Earth was a completely inhospitable place for life: its melting surface was radioactive, water did not exist except as water vapour, and the atmosphere was full of poisonous gases like cyanide and formaldehyde, and deprived of breathable oxygen.
About 3.9 billion years ago, the Earth's surface became cool enough to form a thin crust lying on the fusing magma. Strangely enough, life - and therefore DNA - appeared relatively quickly after this. There are sedimentary rocks which indicate possible bacterial deposits about 3.8 billion years old, and true microbial fossils which date back 3.5 billion years.
During the first two billion years of life, there were only anaerobic bacteria on Earth, which regarded oxygen as poison. Living in water, some of them had learned to use hydrogen and to expel oxygen contained in the H2O molecule, activating new metabolic pathways which were more efficient in energy terms. The gradual enrichment of oxygen in the atmosphere permitted the apparition of a new type of cells capable of using oxygen and provided with a nucleus to regroup DNA. These nuclear cells are much larger than bacteria, at least thirty times more voluminous. According to biologists Lynn Margulis and Dorion Sagan: "Biological transition between bacteria and nuclear cells is so sudden that it cannot be explained by gradual changes in time."
Ever since that moment, life as we know it took form. Nuclear cells associated to form the first multi-cellular beings, such as algae. These also produced oxygen by photosynthesis. Oxygen rates in the atmosphere reached about 21%, a level that seems to have been fortunately stable for the last five hundred million years, since a bit higher percentage of oxygen would cause living creatures to ignite spontaneously. For Margulis and Sagan, this fact "gives the impression of a conscious decision to keep the balance between danger and opportunity, risk and benefit."
About five hundred million years ago there is an explosion of life in a true lavishness of multi-cellular species, algae, more complex plants and animals which not only live in water, but also on the ground and in the air. None of the living species of those days subsist nowadays. According to some calculations, almost all species that have existed on Earth have already disappeared, while currently there are between three and fifty million species on the planet.
DNA is a master of transformation: life based on cells informed by DNA has formed the air we breath, the landscape we see and the disturbing diversity of living beings which we are a part of. In four billion years it has multiplied itself in an incalculable number of different species, rigorously remaining the same.
Inside the nucleus, DNA forms curves and unrolls itself, it contours and oscillates. Frequently, specialists compare the shape and the movements of this large molecule with the ones of a serpent. Molecular biologist Christopher Wills, for example, writes: "The two DNA chains are similar to two intertwined serpents in a kind of love ritual."
In sum, DNA is a master of transformation with serpent shape, which lives in the water, at the same time long and minuscule, simple and double. Such as the cosmic serpent.
In fact, the genome or necessary information to build a human being (for example) is in three billion letters displayed along a single DNA thread. In some places this thread wraps around itself to form twenty-three more compact segments called chromosomes. We all inherit a complete set of chromosomes from our parents and so we possess twenty-three pairs of them. Each chromosome is formed by a very long thread of DNA which is basically a double message, with the main text in one of the ribbons of the double helix and its complementary duplicate in the other ribbon. In this way, all our cells contain two complete genomes as well as their copies. Our genetic message, therefore, is twice double and contains a total of six billion pairs of bases or twelve billion letters.
The DNA contained in the nucleus of a human cell measures about two metres. Along its length, the two ribbons of the double helix coil around themselves hundreds of millions of times.
At the level of its material aspect, or its shape, DNA is thus a doubly double text that wraps around itself, in other words, a twisted-twisted language.
Reading enzymes only read DNA segments that codify the construction of proteins and enzymes. These segments, called genes, only represent 3% of the human genome. The rest 97% is never read; its
usefulness is a mystery.
Biologists Chris Calladine and Horace Drew sum up the situation: "The largest part of DNA in our body does things we do not understand at the moment."
DNA is the key to life that possesses the shape of a long simple or double serpent, or a tressed linen wick, that allows passing from one to many and it is located in water.
However, this is just a group of clues that every investigator, or member of the jury, is free to interpret.
|Essay about the Book "The Cosmic Serpent"|
of Jeremy Narby by Patricia Burgos