Clear the Mud

The intro to this attempt at being a smarty-pants who knows less than he thinks is here.
Please read that first, so you can get the context of where I'm coming from.
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Quiet Accumulations

To recap from the first post: You, and everyone you know is a mutant.

And remember the basic description:

• DNA is the instructions, written in a simple alphabet, that says how to build proteins.
• Proteins are the things that actually go about building you.

Most mutations neither harm nor help:

If we all start with a couple of hundred mutations in our DNA, why don’t we all have three arms and twenty eyes - or at least look like Hugh Jackman?

I suppose it's worth making a semantic distinction here. In saying "mutation" and "mutant", I am referring to spelling changes in your DNA instructions (the mutation) and the protein or organism which is encoded by the altered DNA (the mutant). And that is typically exactly what is meant by those words.

However, most of us think of a "mutant" as the end result - some person with a demonstrable change from the norms of humanity - a six-toed foot, for example. Using that more common usage, then probably not everyone is a physical mutant. Although, changes from the norm are often not in things visible to the eye, so you never know.

So, here’s the deal: most genetic mutations have no major effect on how you function as a human or how you look, at least compared to the normal variations seen throughout humanity.

In these cases - again the most common - the net result is that there is no discernible difference between how you function with that mutation and how you would function without it. It is a fact of statistics and the way DNA and proteins work that most mutations will not actually cause any real problem or benefit at all.

It's the same difference:
In many cases, this “no harm, no foul” result is because the particular mutation in the DNA instruction causes absolutely no change in how the proteins – the actual machinery and materials of you - are built. This is called a “silent” mutation.

There’s a detailed reason that this is possible - but for now, just think of how you, a reader of English, would interpret the words “color” and “colour”. Depending on where you live (the US or UK), one is probably the preferred spelling, but you know that they both mean the exact same thing – it’s just a minor spelling variation about which most English speakers are forgiving.

Essentially the same thing happens with many words in DNA instructions. There are quite a number of DNA words that can be spelled with minor variation and yet mean precisely the same thing.

So mutations in DNA that simply result in accepted spelling variations will not change the protein that it encodes in any way at all.

Close enough for government work:
Other times, the change is not a simple spelling variation but actually does alter how the protein is built. However, even with a change in the structure, many changes are minimal enough to actually keep the protein functioning in approximately the same way as the original. This is termed a “neutral” mutation.

Imagine you had instructions to make a chain to lock a bike to a bike rack. The instructions call for 50 metal oval links and a very intricate lock mechanism on one end.

And the instructions are not in the shorthand we might be used to, like this:

Link 50 metal ovals together, add lock on the end.

The instructions are more linear, step-by-step, no matter how repetitive it seems, like this:

Start - add metal oval - add metal oval - add metal oval - add metal oval - (this is repeated 46 more times)

Followed by the (likely) hundreds of individual steps to make a lock from scratch, attached to the chain of links, and then it's done.

Now, imagine the instructions got slightly garbled so it suddenly said to do this:

Start - add metal oval - add metal oval - add metal SQUARE - add metal oval - (this is repeated 46 more times)

Well, a metal square link isn't quite the same as a metal oval link, but it still serves the purpose of being a solid link, and the chain is about the same length – so, in the end, we still have a perfectly usable bike lock system.

These "neutral" mutations happen quite often. And, in these cases, it’s almost as harmless a change as the previous type of silent mutation.

( Note: A very different outcome might have happened had we mucked about with the very intricate makeup of the lock mechanism, or if a metal link had been replaced with a link made of silly putty.)


Sooner or later... the day comes when you can't hide from what you've done anymore. A day of reckoning.

As mentioned previously, at conception, every human child is a recipient of a couple of hundred of these type of mutations. Now, considering your DNA instruction set is made up of a few billion letters, this is an almost imperceptible amount of change.

And because silent and neutral mutations, introduced one by one in the DNA instruction book, are often not even noticed, this allows genetic mutations creep into a population over time.

But over time, over many generations, it begins to add up. Think about this:

You inherited a few hundred mutations from your parents.
You give all of those plus a couple hundred more to each child you might have.
They give yours and your parents’ mutations to their children.
And those children (your grandkids), in turn, give the mutations from your parents, you, your child, and themselves to your great grandchildren.

And it goes on.

And this has always been happening since before we were born and will continue to happen long after we’re gone.

And those are just the simple spelling errors. There's far more dramatic mutations out there as well.

Because of all this, the changes accumulate.

And, again, many of these end up being no benefit and no harm.

But at some point, for one of many reasons, a mutation - be it a brand new one or a combination of older ones - will make a difference.

For one of your descendants, who knows how many generations away, this accumulation of mutations could ultimately lead to something very harmful.

Or, almost as likely, they could result in something that will save their life and the lives of *their* descendants.

Or it just might make their eyes bluer.

You really won’t know until the day that it kicks in.

But that day (or many days, or century, or millennium) ends up being very important.

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Working topics for subsequent posts (Just so I have it down in print. And so people can say, "hey you never wrote that one!"):

• We are the things that worked
• The tiny difference between life and death
• The confusion of language: "The theory"
• The confusion of language: "The fittest"
• There's always something new
• You think living is easy? (The Second Law of overlooking the obvious)
• ...?