Some very imaginative minds are turning their attention to the mechanisms inside the human cell, and not before time – molecular biology is proving to be, by far, the most fascinating and relevant field of research for humanity.
Far more than the exploration of space or the subatomic world, what we discover about our own marvellous construction shows us how modern ways of life are wrecking it; there isn’t a single aspect of society whose improvement doesn’t depend in some way on a better understanding of our biology.
For example, recently it was shown that benevolent thought increased vagal tone, and internal modes of happiness activated genetic switches to affect our physical health. It has been known for a while that meditation affects chromosonal longevity, and that a raft of other benefits proceed from various practices formerly thought to be arbitrary ideas associated with spiritual thought.
In their drive towards ever tinier electronics, researchers have looked at DNA as a storage mechanism which dwarfs that of human technology. Nick Goldman at the European Bioinformatics Institute found that a single gram of DNA can carry 2 petabytes (2 billion gigabytes) of data.
This means if a single DVD (at 11 grams) carries 5 gigabytes of data (enough for 2.5 copies of Iron Man III) then one gram of DNA outperforms 400 million DVDs – 4.4 million kilograms’ worth (4,850 US tons or 4,400 metric tons) of typical DVD data technology. That weight is about the same as four thousand elephants, or 145 Sherman tanks, or the Pantheon in Rome – the third largest masonry building in the world.
That’s spectacular in itself but, as Goldman points out, DNA has the added advantages of being permanent and independent of changing format styles. DVDs, like tapes and magnetic disks, degrade very quickly, and in fifteen years all the digital media you have now will be broken or obsolete. DNA on the other hand lasts for thousands of years, and its language is unchanging, its coding language (the specific mapping of codons to amino acids) not arriving by trial and error but the same now as it was at the beginning of life on Earth, at least 3.5 billion years ago.
Interestingly, in 2009 DNA fragments were detected from cells within a fossilised dinosaur bone at least 160m years old (MH Schweitzer, 2013 Molecular analyses of dinosaur osteocytes support the presence of endogenous molecules. Bone. 52 (1): 414-423) showing that DNA may be a lot more persistent than we first thought.
The DNA within our cells functions not just as a chemical system, but an electrical one. And this means it’s highly sensitive to electrical damage, needing dedicated mechanisms within the cell to effect repairs.
For example, free radicals attack DNA by stealing an electron from one of the chemical bases of DNA. That base pulls an electron off a neighbouring one and the resulting electron hole zips along the DNA like a positive electrical current, and degrading the encoded data. This explains why certain electrical disturbances can cause the onset of cancer. It has long been ignored that cancer incidences spike in communities living near electrical pylons, and a recent protest in Italy took place exactly because of this kind of problem:
A group of activists occupied the high-frequency US military satellite system located on Naval Air Station, Segonella. The clashes were triggered by the news that cancer rates have risen exponentially among the local population since the installation of the MUOS station, due to long-term exposure to high-power transmissions.
Certain radio frequency bands between 15-60 Hz have been found to promote cancers, corrupting mRNA functions and therefore the manufacture of proteins, and also immune responses and intercellular communication (Adey, 1992). All of these have a direct bearing on cancer.
Some of the “junk” DNA comprises pairs of adenine and thymine, which act as insulators to protect coding genes. So they’re not junk, and not disposable: Jacqueline Barton of the California Institute of Technology has shown that DNA also uses its own electrical properties for protection. At the edge of some genes, there is a string of G letters (guanine). They stop the travelling electron hole in its tracks, deflecting the damage from the protein-coding parts of the DNA.
One writer has suggested that the part of the DNA coiled around protein structures called histones may exhibit electronic inductance:
As a coil, it has electronic inductance, and since we have a series of coils, we have a series inductance circuit. DNA current passes initially through the helix in a state where it can discharge its field energy.
Hence we have a pulse within the DNA interacting with other biomolecules like the membrane. The pulse can go in and come out, and the DNA is not imperiled (Garnett, 2000)
Undamaged DNA conducts electricity, while an error blocks the current. But Barton has found that the cell has enzymes which take advantage of this to effect repairs. They behave like linemen checking the signalling integrity of wiring: working in teams, a pair of these enzymes lock onto separate parts of a DNA strand, one sending an electron along while the other waits to receive it.
Once it receives the electron, the receiving lineman detaches, signalling the intermediate length is problem-free. Knowing how quickly electrons can travel – esepcially over such tiny distances within stretches of DNA – you can imagine how fast these characters work and how accurate they have to be.
If there is a break in the transmission, the electron doesn’t reach the second enzyme and somehow it already knows how long it should wait for, so it travels along the strand towards the first enzyme until it reaches the error, and then fixes it. This mechanism of repair seems to be present in all living things, from bacteria to man, meaning it must have been with us from the very start.
Curious Coils: How does DNA fit into a cell?
Although exact estimates vary, we know about 2.5 metres (2,500mm) of DNA is stored inside a restricted area within a cell which is itself roughly 20 micron in diameter – the size of a grain of talcum powder, or one fiftieth of a millimetre.
This is the same as storing a 5 kilometre length inside a ping pong ball. How is this possible? The twisting of the strand could account for a 35% reduction in length (to 1,625 mm) but the real compression is performed by an utterly fantastic system of alternating coils and twists.
The already-twisted DNA coils twice around a spool formed of 8 positively charged proteins called histones, forming what’s called a nucleosome. This reduces the DNA’s length by as much as 85% – (243mm – try this with a tape measure around a tube and see!) – and then the nucleosomes are grouped in circles of 6, making the assembly’s total length a more manageable, but not yet microscopic, 40mm in length – about the same as the first joint of your thumb.
This dense 30 nanometre data fibre (one nanometre is 1 thousandth of a micron, or one millionth of a millimetre) is twisted again, with the thicker fibre coiled. After that I estimate it would need two further twists and coils to reduce the whole thing to a length of .41 mm or 410 micron, which is divided (unequally) into 46 chromosomes, each of which is doubled over on itself. The average length of each chromosome would become a more manageable, and quite microscopic, 4.5 micron.
I’ve made a few guesses about this, and there must be more ingenious stages in coiling than I’ve supposed, but the idea that so much crucial data is compressed into such a tiny space is utterly fantastic. Though it avoids explaining some later stages, a beautiful video on DNA coiling is available here.