#SignalDegradation

Soundtrack: the opening theme of “The Big Bang Theory”

 

error-102075_1920

When I was in university I majored in Earth Sciences and Biology, thinking this was some sort of suitable compromise with my then academic ambitions. You see, I’d really wanted to study palaeontology. It had been one of those vague childhood longings that had not quite managed to be squeezed into a torpor by life. Having these two majors seemed to make sense. For part of the day I was studying geology, geophysics and sedimentary processes.  For the remainder I was buried in lower eukaryotes,  molecular and microbiology and animal physiology. Dinosaurs are somewhere in the midst of all that, right?

Kind of. Well the dinosaurs fell by the wayside (became extinct?) and I found myself really liking pretty much everything else I was studying. Learning is a joy in itself. Whilst in university I was privileged to attend lectures given by Dr Leigh Burgoyne. For those unfamiliar with molecular biology Dr Burgoyne is half of a pair of scientists who elucidated the structure of chromatin.

What tha’ heck is chromatin? Chromatin is a complex of structural proteins that enable Deoxyribose nucleic acid (DNA) to play the ultimate game of Tetris. DNA is a very wily molecule, which I’ve touched on in a previous post. It has insane data storage potential, and a single strand of DNA is three metres long! Now you understand why it needs some mad packaging skills to squeeze into something the size of one of your cells. That’s basically what chromatin does.

cube-2026724
Life wouldn’t work if it didn’t have an epic case of OCD.

 

I remember a single lecture given by Dr Burgoyne. To be honest, I remember very little of about nine-tenths of it (it’s still stashed in my head somewhere), but then it seemed like he really began speaking.

He told us the tale of life….

In order to parse what he told us I need to paraphrase what he said. I need to mix metaphors and go off on tangents.

Now, any students of science out there will have butted heads with statistics and probability whilst studying. I’m not in any way being elitist here. Most sane people know that the universe is a collection of freakish accidents all cycling constantly and spewing out more freakish accidents. Somehow, a stream of such accidents has led to you. As Terry Pratchett said in one of his Discworld novels;

Million to one chances happen nine times out of ten.”

train-wreck-67775_1920

We are all freak accidents. Every single person- every single thing– alive today is a current iteration of a single freak accident that took place in a warm, shallow pond nearly 4 billion years ago. Or trapped inside ice. Or on the slope of a deep-sea hydrothermal vent. On a sheet of clay even.

Hell, maybe it was on the shifting gravel filled terrain of a passing comet. Who knows? I’m sure not going to be presumptuous. Theories on the origin of life abound. I strongly suggest venturing out into the literature and checking these out for yourself.

Freak accident.

That accident somehow decided it wanted to keep on keeping on. So it went looking for other freak accidents to consume. This in itself required some changes. And so it began.

Life.

Life is not just a thing in itself.  Life is all of the things that life does. Emergence gave us life.

Life got hungry. Life went looking. Life grew. At some point life joined forces with other life, going onto business. These partnerships have lasted till this day. Life became stronger, faster. Like human explorers expanding forever westwards life travelled. It began to see. It began to conquer. The entire planet was a vast new frontier. A planet of accidents and danger. At every single turn life met with struggle, and it was forced to sink or swim.

So it either sank or swam. You’re only here right now, sitting on this train, or hiding in the toilet for a few minutes because every single one of your ancestors swam. If the theory of a multiverse holds any water, then in another universe it’s someone else reading here in this spot. Or I never existed to write this and you’re watching a Minecraft walk through on YouTube instead. Whatever floats your boat.

I remember the lecture. Dr Burgoyne gave his thoughts on the astronomical run of good luck that led to everyone being in that lecture theatre. I swear, you could have heard a pin drop. People were listening. It was an amazing moment.

university-105709_1920
NOT the lecture in question, but you get the picture..

What’s more amazing than the fact that we are here at all? The fact that in nearly four billion years of life, the central message of life has only degraded by a few percent! That’s just nuts! Think about it!

DNA (sometimes RNA) is the information storage molecule for all life. RNA stores the genetic information within viruses, which inhabit a shadowy world somewhere between the living and the abiotic world. For the sake of simplicity I will refer only to DNA.  We’re all scientifical enough to not get all Sheldon Cooper when I hold up DNA  as THE information storage molecule.

Moving on Ben.

Think of life as a signal, and DNA is the filter, tuning out cosmic background clutter and refining it into something pretty improbable. Like you. At a point in time the signal was set in motion. Whether it was in a pond, an iceberg or a comet, life got going; using some kind of information storage in order to send copies of itself out into the big bad world.

That signal’s been around for a very long time, replicating and transcribing and reinventing itself in an endless profusion of forms. Some very ancient cellular machinery has been hard at work, replicating DNA with incredible fidelity. What amazes me about all of this is that cellular automata (proteins for the most part) carry out this herculean task. Proteins aren’t alive. They are essential players in the mechanics of life, but they aren’t alive in themselves. Some proteins are capable of replication, but that’s another post in itself (and an interesting one too).

Let’s play the Pepsi taste challenge, but instead of cola drinks let’s compare say…YOU and a bacterium. That seems a bit silly, right? There couldn’t possibly be two more different organisms on the face of the planet. Let’s put aside the fact that your particular body is about ninety percent bacteria in terms of numbers. Let’s focus on the ten percent of you that’s actually YOU. Ok. You have eyes, ears and wear pants. You’re reading this post on a phone, computer or tablet.

Keyword: Reading.

Implication: highly complex brain along with associated neuronal infrastructure, from which emerges this nebulous thing called a consciousness. You can’t point at it, but you know it’s there.

You wear clothes. I wear warm clothes right now, because it’s a cold day. You’re probably drinking or eating something right now. I’m sucking down a coffee. Implications of this: you have a digestive system, along with associated waste disposal mechanisms. You have fingers, and nostrils to stick them up sometimes, leading to lungs. You can drive a car. Other creatures like you have walked on the Moon and made brainless YouTube videos.

Bacteria, by comparison to you, are a little simplistic right?

bacteria-62993_1920
E. coli. Doesn’t seem too impressive, right?

Hah!

Time to shatter some illusions. You may have heard that human beings and chimpanzees are 98 percent genetically identical. Only 2 percent of your DNA makes you human, compared to a chimp. Well, brace yourself.

You and that bacterium you look down upon so loftily differ genetically by 10 percent. TEN percent! In nearly four billion years, bacteria, one of the oldest lineages of life to exist, have barely changed. All of those changes have been tiny and incremental, giving rise to the kaleidoscopic variety of life that runs, flies and swims across this planet now. That’s pretty amazing. Just knowing something like that feels like being privy to some cosmic secret. Hell, I think it is.

bacteria
Ha! Thought you were hot stuff, didn’t you?

Let’s keep going with this biological Pepsi taste challenge.

Can you keep gossip to yourself? We live in an age where information and reality are becoming blurred. The very existence of Alt-news, Alt-facts, false news, filter bubbles and a host of other ills plaguing the last few bastions of enlightenment are nothing new. Have you ever played the game of Chinese whispers? I’m Australian, so it may be called something different where you come from. A story is spoken, or whispered into the ear of a player, who whispers it into the ear of the next, and so on. It’s fun to see how the story spontaneously mutates, changing as it goes. Sometimes it reaches the final person in the line a completely new beast. This string of mutations happens quickly, completely changing the original story, and all in a few moments.

twitter-292994_1920
Social media. It has a weapons grade case of Chinese whispers….

Think of your genetic information, or genome, as a book. Blindly and efficiently this book is replicated. The two entwined threads in it’s double helix are unwound by DNA helicase. Then DNA polymerase attaches to the strands, and attaches complementary nucleotides to their respective exposed base pairs along the strand. This is an extremely cut down version of what happens, but all you really need to know in the context of this post is this: it all happens extremely quickly. In the bacterium Eschericia coli, replication can speed along at the rate of around 1,000 nucleotides per second. DNA polymerase in your cells works much more slowly, at a snail-like 50 nucleotides per second. Such speeds are achieved by many polymerases attaching to unfettered DNA strands. Many hands make light work after all. How much can you achieve in one second? All of this goes to show that parallel processing is one of Nature’s oldest tricks.

You’d be completely reasonable to assume that such a process would be fraught with errors. It is. But unlike the game of Chinese whispers, or the rant on Facebook, errors of interpretation and transcription happen much more infrequently. After all, if DNA replication was untidy and prone to errors life would have eventually never taken off. Early in the piece evolution made sure that efficient replication of information was critical. Some mutation is good, but too much is bad. A few mutations here and there over the eons have given rise to you. Too much mutation and life breaks down. So what constitutes a few mutations here and there?

spag
Without organisation and proofreading, life would maybe have made it this far….

For every 10 billion base pairs that are replicated, approximately 1 error gets through. DNA polymerase on its own is pretty good at what it does. Being completely automatic it doesn’t have a pesky brain doing bothersome things like over thinking or day-dreaming. It isn’t perfect, however. Left to itself, DNA polymerase will stuff things up to the order of 1 bad base pair in every 100 million replicated. A suite of repair enzymes are at its disposal, tidying up these mistakes and getting replication fidelity up to the 1 in 10 billion mark.

Boy, talk about an amateur. Me, that is. I’m a chef by profession. After 22 years of sweating it out in kitchens, I still manage to burn at least one piece of bread a day (don’t tell anyone). If pieces of toast were living things, then at my hands not only would they never evolve, they would become extinct long before they ever had a chance. Maybe they should have enzymes working in kitchens.

Maybe not.

So, I hope you see what I mean. Every single living thing on earth (and who knows where else) exists purely because extremely high fidelity of replication has evolved to ensure against excessive mutation. Another way of putting it is; even after four billion years of nearby supernovae, disasters, extinctions, geochemical catastrophes and endless strife, life has been able to hold on, and all because of extremely faithful data storage and propagation. If we ourselves can evolve past our own tendency to conflate every thing we hear and describe, maybe we could stick around for a while longer too.

Life is a signal, a signal that can’t be broken. Let’s learn from it.

 

Ben.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s